Office rents in Hong Kong's skyscrapers remain the world's highest at US$250.50 a square foot a year, according to property consultant Knight Frank.

Skyscraper prime office rents in New York have shot up 20 per cent to US$150 per square foot, making it the second-most expensive city, followed by US$124 per square foot in Tokyo. The survey defines skyscrapers as buildings more than 350 ft high.

In terms of rent rises, Hong Kong was third-fastest, with a year-on-year gain of 11.3 per cent in the second half of last year, trailing New York and Frankfurt, where rents rose 13.2 per cent.

"Grade A office rents in the core areas of Hong Kong are expected to rise a further 5 per cent this year due to limited supply," said David Ji, the head of research and consultancy for greater China at Knight Frank.

JLL head of research Denis Ma said monthly rents at Two International Finance Centre - the tallest building in Central - were HK$130 to HK$155 a square foot, depending on the office size.

Ji said grade A office rents in Beijing, Shanghai and Guangzhou were, however, expected to fall as abundant supply would come on stream this year.

"This is reflected in the ranking of these first-tier Chinese cities, with Shanghai ranking only 10th globally, and Beijing falling out of the top 10," he said.

In 2009, there were 19 skyscrapers in the world that were taller than 1,000 ft, the report said. Today, there are 79, with 40 per cent in China.

"The expansion upwards in the major Chinese cities has been a remarkable phenomenon over the past decade," said Nicholas Holt, the head of research for the Asia-Pacific at Knight Frank. "The fact that 40 per cent of skyscrapers in the world are in China underlines the growing importance of the country's economy on the world stage."

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Stunning new video shows a 57-story building being constructed in only 19 working days.

Broad Sustainable, the builder, was able to get Mini Sky City ready so quickly for occupants in the central Chinese city of Changsha by assembling the skyscraper out of pre-fabricated sections. It was put together at a rate of three floors per day.

"With the traditional method, they have to build a skyscraper brick by brick, but with our method, we just need to assemble the blocks," company engineer Chen Xiangqian told the Associated Press.

More from the AP:

The Changsha-based company spent 4 1/2 months fabricating the building's 2,736 modules before construction began. The first 20 floors were completed last year, and the remaining 37 were built from Jan. 31 to Feb. 17 this year, Xiao said. The company has honed its technology to accelerate its construction speed from two floors to three floors a day, he said.

Mini Sky City has 800 apartments and office space for 4,000 workers, according to the report.

The building is said to be sturdy enough to withstand an earthquake, though it is not clear how strong a temblor it could endure.

Broad Sustainable previously claimed to have its sights set on throwing together a 220-story building in only three months. But that structure has yet to be built.

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Watch these photographers climb a new skyscraper in China. The tower is currently 2,073-feet feet tall and is the second-tallest skyscraper in the world. 

Video courtesy of On The Roofs 

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Every city in the world has a unique skyline. But is it possible to say which is the best?

The international building database Emporis attempts to quantify skylines by looking at the number and height of buildings in the world's major cities. The result is an ever-changing ranking of the world's most impressive cityscapes.

To rank skylines, Emporis looks at completed skyscrapers (40 floors or more) and high-rises (12 to 39 floors), and assigns each building a point value based on its floor count. Taller buildings receive significantly higher values (see Emporis' complete methodology here). TV towers, masts, bridges, and other structures are excluded.

Moscow jumped from 11th place to fourth place year-over-year, and Shanghai (No. 8) overtook São Paulo (No. 9).

No. 25: Rio de Janeiro has 2,595 tall buildings in 1,182 square kilometers.

Methodology: Each building over 11 floors was assigned a point value based on number of floors. Measurements exclude TV towers, masts, bridges, or other structures.

Source: Emporis

No. 24: Osaka, Japan, has 1,490 tall buildings in 220 square kilometers.

Methodology: Each building over 11 floors was assigned a point value based on number of floors. Measurements exclude TV towers, masts, bridges, or other structures.

Source: Emporis

No. 23: Jakarta, Indonesia, has 443 tall buildings in 661 square kilometers.

Methodology: Each building over 11 floors was assigned a point value based on number of floors. Measurements exclude TV towers, masts, bridges, or other structures.

Source: Emporis

Emporis, the international building database, recently ranked the best skylines in the world.

To do this, Emporis looked at the number and height of buildings in major cities around the world. Dadaviz then took these rankings and created a map showing where the top 40 skylines in the world are located.

Hong Kong was rated number one, followed by New York City. Makati (in the Phillipines) and Xiamen (in China) made up the bottom of the ranking.

Take a look at the map below to see where the skylines of other major cities ranked.

SEE ALSO: The 25 best skylines in the world (ranked!)

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One World Observatory — the skydeck at One World Trade — finally opened to the public this weekend, and people were lined up for hours to see New York City from a new perspective.

Perched at 1,250 feet above the ground, the newly-opened observatory attracted tourists and locals alike, all with cameras and smartphones in-hand. 

We scoured Instagram for the best photos from opening weekend. Here's what we found: 

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The 127-story Shanghai Tower is now the tallest building in China and the second tallest in the world. From breaking ground to completion, the building took almost seven years to complete.

It stands 2,073 feet high, behind only the Burj Khalifa in Dubai (2,717 feet). 

Produced by Jason Gaines. Video courtesy of Associated Press.

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This time-lapse video by Earth Cam shows the construction of One World Trade Center from October 2004 to Memorial Day 2015. Hundreds of thousands of high-definition images were captured over the past 11 years to complete this beautiful time-lapse.

Video courtesy of Earth Cam

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London's skyline is about to get more cramped.

There are more than 230 new towers over 20 stories tall planned across the capital, according to New London Architecture (NLA), an independent think tank in the UK.

NLA has pulled together a selection of tall buildings that were either completed this year or are expected to be complete within the next decade.

You can see more images, models, and interactive displays of the planned growth at the NLA's London's Growing Up exhibition, which is on display until Thursday, June 12.

The Quill is a 31-storey tower in Southwark that will provide student housing for King's College London. The Quill is a reference to the area's literary heritage. There are also curved structures at the top of the building that resemble a quill. The building is expected to be complete later this year.

Vauxhall Square in Lambeth will include two hotels, two office buildings, and two residential towers. A 50-bed homeless hostel will also be part of the building cluster. A large new public square with plenty of pedestrian paths will be at the center of the site. The Square is expected to be complete in 2018.

These twin 40-storey towers, known as The Blades, are still in the design stage and are planned for a site in Elephant and Castle. They will be engineered to slice through the wind to provide a shield to pedestrians below.

Anyone who has seen Pixar’s incredible 2009 animated movie “Up” will realise this tiny house in Sydney is the real life equivalent — just without all the balloons.

Sandwiched between two mammoth skyscrapers in the business district of St Leonards is family-run jewellery business John Clarke & Son, at 19 Chandos Street.

While it may not look like much the 223-square metre converted home, which was purchased 75 years ago, is expected to sell for at least $3.5 million at auction next week on June 17.

With two street frontages, close proximity to St Leonards train station and the rising popularity of business districts outside the city’s CBD, the property’s real estate agent CBRE says the land is the perfect development opportunity.

Agent Tim Grossman told News Corp: “Most likely it’ll be a mixed use development with ground floor retail and residential units above; 99 percent of enquirers (have been) looking to redevelop in that form.”

The CBRE listing has received close to 450 pages views.

Here it is:

The St Leonard property is just 20 minutes from Sydney's CBD, making it a desirable location for commercial developers looking for a cheaper option near the city.

While it may be narrow the block of land has room to make up for vertically.

The front of the property is located on 19 Chandos Street...

While the back of the building is accessed by Atchison Lane.

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The permitting process surrounding high-profile projects is becoming increasingly convoluted, with ‘dummy filings’ now commonly submitted prior to actual new building applications. This is particularly true at 217 West 57th Street, which still doesn’t have any on-site renderings. But luckily some new supporting documents have been filed with the city, revealing what appear to be the actual height numbers for the tower’s parapet and roof, confirming it will become the country’s tallest building.

The documents show the building’s curtain wall will top out at 1,521.83 feet above street level, meaning 217 West 57th Street will officially stand 71 feet taller than Chicago’s Willis Tower, the country’s current title holder of ‘tallest roof,’ ahead of 432 Park Avenue and One World Trade Center.

A floor count is also now available, and the tower will rise 95 stories.

Besides minor adjustments at the very top, the numbers are all very close to the figures YIMBY had previously reported (which had ranged from 1,478 to 1,530 feet), though even a difference of only one foot could be significant with regards to the rankings, as Nordstrom’s spire may or may not be slated to stand 1,775 feet tall. Anything above that would make it officially taller than One World Trade Center.

Unlike its Downtown rival, 217 West 57th Street will greatly assist the pedestrian experience in its respective neighborhood, as its first couple hundred feet will house a Nordstrom rather than the equivalent of a bunker; floor plans for the store are also available in the new filings. Above that, condominiums will predominate.

Construction work is already making major headway, and opening of the supertall is expected in 2018, though its impact on the skyline should begin to be felt by next year. Adrian Smith and Gordon Gill are the design architects, and Extell is developing.

SEE ALSO: Daredevils climb skyscraper in China

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Broad Sustainable Building, a Chinese architecture company, recently constructed a 57-story, 800 apartment building in 19 working days. 

It's called Mini Sky City. The man behind it is Zhang Yue, a Chinese entrepreneur with an Elon Musk-ian streak for launching revolutions. 

As the BBC reports, Zhang wants to start a revolution in building. 

Which you can see from Mini Sky City's three-floors-per-day construction.

 The full video is nuts.

But as the 'mini' in its name implies, Mini Sky City is just the beginning. 

Broad Group wants to build the tallest building in the world, higher than the Burj Khalifa in Dubai. 

It'll be called Sky City, standing a full 220 stories high.

Founder Zhang Yue tells the BBC that Broad Group will build Sky City in a fraction of the time. While it took the Burj five years to be completed, Zhang says that Sky City will only take seven months.  

It'll come complete with everything you need to "live vertically," like an indoor farm or a helipad. 

The key? A little hack called modular construction.

The Modular Building Institute defines it like this:

Modular construction is a process in which a building is constructed off-site, under controlled plant conditions, using the same materials and designing to the same codes and standards as conventionally built facilities – but in about half the time. Buildings are produced in “modules” that when put together on site, reflect the identical design intent and specifications of the most sophisticated site-built facility – without compromise.

Modular design has been used at a smaller scale for a while now.

We probably know it most intimately through the work of Ikea, a company with a  furniture empire that has come to dominate the world. 

Here's how Ikea describes its sectional sofas: 

The great thing with a modular sofa is that you can create your own combination, so you get exactly what you want. Then you can adapt or add on to what you have if your needs change. And with our big choice of styles and covers, it’s easy to get the look that suits you, too.

Broad Group's skyscrapers are kind of like the Ikea sofas of construction.

As BBC reports, the process for building is the same: steel comes into Broad Group's factories, and it gets welded into modules like a column or cross beam. 

Then those modules get trucked out.

Crane them up.

And snap them into place, Tetris-style.

"With the traditional method they have to build a skyscraper brick by brick, but with our method we just need to assemble the blocks," company engineer Chen Xiangqian told the Guardian. "This is definitely the fastest speed in our industry." 

To read the full BBC feature on Broad Sustainable Building, go here.

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London's skyline is about to get more cramped.

There are more than 230 new towers over 20 stories tall planned across the capital, according to New London Architecture (NLA), an independent think tank in the UK.

NLA has pulled together a selection of tall buildings that were either completed this year or are expected to be complete within the next decade.

You can see more images, models, and interactive displays of the planned growth at the NLA's London's Growing Up exhibition, which is on display until Thursday, June 12.

Click to see the slides »

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Paris has approved its first tower in over 40 years; the city council has agreed to move forward with Herzog & de Meuron's 180-meter-tall "Triangle Tower" - or "Tour Triangle" - after initially rejecting the proposal last year.

The controversial plans have been the center of an intense debate since its unveiling in 2008 on whether or not Paris should preserve its 19-century skyline. 

As Gizmodo reports, the Swiss architects sold the tower to the city by claiming its glass facade will "disappear" into the skyline.

“Almost everything the architects say has one message: This building is invisible,” as Foreign Policy pointed out last year. “As if to reinforce this strange duality, the renderings omit Paris’s one true existing skyscraper: the wildly unpopular Tour Montparnasse, built in 1973.”

Once built, the tower will be Paris' third tallest structure, after the 324-meter Eiffel Tower and 209-meter Montparnasse Tower. It will house a 130-room hotel, restaurant, Sky Bark and 70,000-square-meters of office space.  

The building will be the city's first tower realized after its height limitations were removed in 2010, which prohibited the construction of buildings over 36 meters. 

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Cornell Tech, an applied sciences program out of Cornell University, is building a giant futuristic campus on New York City's Roosevelt Island. But the most exciting part of the campus isn't in the academic buildings or green spaces — it's the dorms. 

The campus's 250-foot tall residential high-rise will be so energy efficient that it could change the way buildings are constructed in New York City, if not the rest of the country. 

The high-rise, which will house 520 people when it's completed in 2017, will be the world's tallest and largest passive-house building, meeting strict energy efficiency standards set by Germany's Passive House Institute.

When all is said and done, it will save 882 tons of CO2 each year compared to a normal building.

That's not much compared to the average yearly emissions of a coal power plant (3.5 million tons of CO2), but start thinking about a future where passive house buildings are the norm, and the emissions savings become significant. 

Passive House buildings use little in the way of energy, heating, and cooling. In order to meet the standards, "You need to have every crack sealed," according to Blake Middleton, a partner at Handel Architects, which designed the building. Essentially, the Cornell building has to be completely airtight to pass muster. 

Overall, the $115 million residential building will use 60% to 70% less energy than other similarly sized buildings. It will also cost up to 5% more to develop — but that money will come back many times over in energy savings. 

Making the building airtight was a vexing problem, both from a structural and a design point of view. When architects design urban buildings — especially condos — they usually highlight sweeping views with floor to ceiling windows.

In order to make that work from an energy efficiency perspective, a passive house high-rise would need a double envelope, basically creating a building within a building. That's prohibitively expensive, so Cornell opted instead for slightly smaller windows. 

"There will be well-sized windows that take advantage of views, but they're not as big as they might be if they were catering to that [condo] market," says Arianna Sacks Rosenberg, a senior project manager at Hudson, the developer behind the high-rise. 

The airtight design, combined with a unique ventilator system that brings in fresh air from outside, means that the building doesn't need much in the way of a heating and cooling system.

But that ventilator system went outside of New York City's building code, so the developers had to get special permission to install it.

Another challenge: getting builders to seal up the prefab high-rise to passive house standards. "It requires a much higher degree of care than is traditionally found in sealing up the envelope of a building for more conventional construction," says Middleton.

In Europe, the passive house standard is used for low-rise buildings, offices, and schools (the Cornell building will beat out a 20-story office building in Vienna, Austria, as the tallest passive house structure in the world). Not so in the U.S, where the standard is generally used only for single-family homes.

Cornell's high-rise could change that.

As Middleton points out, the environmentally-minded LEED building standards raised eyebrows when they were first introduced two decades ago. Now LEED has been adopted into building codes. In New York City, for example, new buildings on city property have to be LEED Silver certified. 

"In a way, it's like we’re beta testing a new model of a car that everybody already knows pretty well, but there are certain tweaks going on, and components in that car that have to be machined better, to fit more exactly," says Middleton.

If all of those tweaks add up to a functional high-rise, then Cornell may have paved the way to a more energy-efficient urban future.

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The foundations of what was planned to be the world’s tallest building are being used as fish farm in China two years after the project stalled, according to a newspaper report.

Construction of the 838-metre tall “Sky City” in Changsha started in July 2013 when billionaire Zhang Yue, the president of Broad Group, arrived in a helicopter for the ground-breaking ceremony.

Zhang had expected the 9-billion yuan (HK$11.3 billion) project to be completed in nine months, using prefabricated building modules, and replace the Burj Khalifa in Dubai as the world’s tallest building.

But work stalled after concerns from regulators over the safety of the skyscraper and its environmental impact and funding.

With no progress on the project in sight, villagers nearby have started to raise fish in its 2.6-hectare water-filled foundations, the Xiaoxiang Chen Bao reported.

One villager started to raise fish in March and has invested over 20,000 yuan in his business. “I raise fish on the construction site. It is not in secret, neither have I ever been stopped,” he was quoted as saying.

On the banks of the pit, some villagers grow watermelons. A road built to the project site is used to dry grain in the sun, the report said.

Zhang returned to the spotlight earlier this year after his company finished the construction of a building dubbed Small Sky City, more than 200 metres high, in an eyebrow-raising 19 days.

At the Boao Forum of business and political leaders in March, he insisted Sky City was not a lost cause despite the local government’s suspension of the project.

“[Construction] shouldn’t be far away. We’ll start soon and complete soon,” he said.

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These daredevils climbed to the top of the 1,000-foot-tall construction site for Dubai's new residential tower, Marina 101. When completed, the tower will stand at 1,400 feet and will be the tallest residential building in Dubai. Keow Wee Loong, an established free climber from Malaysia, and his friends scaled the tower in about 55 minutes. Loong has been known to climb the tallest towers in the world, allegedly knocking out security guards in the process.  

Produced by Emma Fierberg. Video courtesy of Associated Press. 

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A giant in London is melting cars, frying bike seats, and scorching sidewalks.

But it's not Godzilla.

It's a "Walkie Talkie"— the nickname for the 38-story skyscraper on Fenchurch Street in central London.

The glare reflected from the glass-fronted building was so strong that people changed its name to "death ray" skyscraper. 

Now, the $300-million-dollar structure is once again wreaking havoc on the nearby street. The gusts of wind at the base of the building are so powerful that they are blowing people over and toppling signs off the nearby buildings.

"I almost got blown over the other day walking up past the building, when I got around the corner it was fine. I was scared to go back!" a sales assistant at a nearby store told The Capitalist. 

"The wind is so strong on this side of the street we usually have to keep the doors closed so stop the clothes getting blown about,” said another.

It's called the down-draught effect. When the wind hits a tall building, it has nowhere else to go and so it is pushed up, down and around the sides. But the air that is pushed downwards creates a sort of wind tunnel at the base of the building. The result: increased wind speed down the street below. 

The Walkie-Talkie, which opened last year, has 690,000 square feet of office space and a rooftop garden. The glass building expands at the top, which makes it look like a concave mirror — or, well, a giant magnifying glass.  

Soon after construction began in 2011, people complained that the "death ray" building was setting pavements, vehicles, and doormats alight.  

Last year, the developers fitted the Walkie-Talkie with a sunshade to cool things down.  

After the sunshine came the wind. The down-draughts that were recently reported near the building came as a surprise to developers — none of that waspredicted before the bricks were laid.

Skyscraper designs are always tested out in wind tunnels to prevent any damage to structures. However, architects are now focusing their attention on the potential impact of winds on people on the nearby streets, according to an expert quoted in the BBC.

Even as more and more high-rises enhance our skylines every day, maybe developers need to start taking a worm's-eye-view to keep people from getting fried on the sidewalk.    

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Normally you'd never notice it, but all tall buildings sway a little in the wind.

Scarcity of land is forcing us to build skyscrapers taller and build them on smaller and smaller bases. But the taller and the skinnier a building is, the more likely it is to sway at the top.

To minimize the swaying, developers are putting giant counterweights called tuned mass dampers (TMDs) near the top of skyscrapers. A TMD is a giant ball made of steel or concrete that weighs anywhere from 300 to 800 tons, and it's usually suspended in the building using springs and pistons.

It looks like this in the Taipei tower in Taiwan:

On a windy day, a skyscraper over 1,000 feet tall might sway a couple of inches, according to Rowan Williams Davies and Irwin, consulting engineers. Usually that movement is imperceptible, but on a particularly breezy day, you can feel the building moving. The sway of some buildings is enough to make the tenants feel sea sick.

So when a big gust of wind blows, the damper swings to balance out the push.

But dampers don't really have anything to do with the structural integrity of a building, according to engineers. They're not, say, stopping the building from falling over. They're only put in place to keep the building's occupants from feeling unnerved or getting seasick.

What about typhoon-force winds?

Back in 2004, the 1,667-foot tall Taipei 101 tower was the tallest building in the world. It's since been eclipsed by other buildings:

It may not be the tallest building anymore, but on Saturday Aug. 8, Taipei 101 set a different record. Or rather its damper set a record when it swung a full meter to counteract 100 mph winds from Typhoon Soudelor, according to Popular Mechanics. One gust clocked in at 145 mph.

A meter might not sound that impressive. Here's a few things to keep in mind while you watch the video footage:

1. This damper is 18 feet across.

2. It weighs 728 tons.

3. Not all of the movement in the video is from the damper itself. Some of it is the building itself moving around the damper.

Skyscraper physics

The New York Times has a great graphic explaining how dampers work. Really though, it all boils down to simple physics.

A skyscraper is like a giant tuning fork. If you give it a good whack, like with a gust of wind or an earthquake, it'll start vibrating at a set frequency. So when the tower is hit with a powerful gust of wind, the damper swings with the same frequency as the building, but in the opposite direction. It doesn't completely stamp out the vibration, but it does keep it under control.

There's a fairly simple equation that physicists and engineers can use to calculate how big to build the damper for each skyscraper.

Another way to think of it is to use the equation "force equals mass times acceleration". If some force acts on a skyscraper — like wind — the occupants are going to feel some kind of acceleration. That acceleration is what causes some people to feel woozy, according to The Constructor.

It's not so much the displacement of the building itself that contractors are concerned about — its the rate of acceleration and deceleration of the building's sway. It's sort of like riding in a subway car. As the train barrels down the track, you don't feel very much. But the second the brakes kick in, you feel a jerk.

These super-tall skyscrapers are a testament to modern engineering, but lets hope that Taipei 101 record isn't broken any time soon.

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