The company hoping to build the world's tallest skyscraper in record time held a groundbreaking ceremony on July 20, in Changsha, China. Broad Sustainable Building is planning to build the 838-meter Sky City using its prefabricated modular construction method. The founder of parent company Broad Group Chairman Zhang Yue announced the tower will be completed by April 2014 and will cost around US$ 846 million to complete. Its total built-up area will contain just over 1 square kilometer of space. The tower, which will be taller than Dubai's Burj Khalifa by 10 meters, will contain a hotel for 1,000 guests and housing for up to 31,400 people, ranging from penthouses to high-density units for low-income tenants. It will also contain a hospital, schools, shops, restaurants and offices, creating an entire city within the building. According to Broad Group, 90 percent of the building will be pre-fabricated in the company's factories. The units will be produced by 20,000 workers in four months. Then it will take three months for 30,000 workers to finish fabricating the units and other actual constructions on site. In its promotion of the project, Broad Sustainable Building frequently cites its environmental credentials, stating that a typical Sky City resident's CO2 production will fall to two tons annually, compared with an average of 5.5 tons per person in China generally. At first about this project announced The Morning Whistle newspaper in 2012. At that time nobody believed. China's new propose is unbelievable, as world's current tallest building Burj Khalifa required six years to build . Two months after shocking news, the head and founder of Broad Sustainable Building Company Zhang Yue, much increases the likelihood of the realization of this incredible project. During the interview, a Chinese man said that the 220-story skyscraper, which he called "Sky City" certainly to be built. In addition, he presented to the public another ambitious project, which height is 2 kilometers. On May 2013 Lloyd Alter at Treehugger reported, that Broad Sustainable Building, the company behind the tower, will begin construction on the prefab behemoth this June. Finally construction begins! Probability that the Broad Sustainable Building Company can afford this unbelievable task is very high. Recently the prefab Hotel in China's south-central Hunan province standing 30 stories was erected in an incredible 360 hours or in 15 days. The hotel built Chinese sustainable-building firm Broad Group and the building is designed to withstand up a 9.0 magnitude earthquake - and even boasts energy-efficient building techniques. In 2010 Broad Group during 6 days built another prefab building, the 15-story Ark Hotel in the Changsha Province, demonstrating fantastic speed of prefab building construction. When completed, the tower would join a growing list of top architectural feats in China. The country is now home to the world's longest high-speed rail line , highest and longest tunnel-to-tunnel bridge, largest building (by area), and soon the world's longest undersea tunne soon the world's longest undersea tunnel.

As soon as 2014, the Burj Khalifa may no longer be the tallest building in the world. Sky City, a planned 220-story prefab tower in Changsha, China, will soon claim that title. According to Lloyd Alter at Treehugger, Broad Sustainable Building, the company behind the tower, will begin construction on the prefab behemoth this June. The energy-efficient skyscraper will literally house an entire city using just 10 percent of the site area, and it could serve as a model for sustainable urban development of the future. Sky City will be prefabricated off site in three months, and it will then be assembled in just seven months. Reaching up 838 meters, the 220-floor tower will feature residential, office space, organic farms, recreation spaces, schools, a hospital retail and much more. The tower will house 4,450 families in apartments ranging from 60 square meters to 465 square meters with 92 elevators at your disposal to reach them. As its name suggest, Sky City will be a vertical city that will accommodate 100 thousand people and offer everything that is needed - water, electricity, sewage, open space, schools, health care and more. Using just a portion of its site, Sky City will be home to the most extreme urban density we've ever seen. But the difference between Sky City and say, Hong Kong, is that the tower will be surrounded by parks, meaning that every resident will have access to open space. The prefabricated tower will include many energy efficient strategies like 20 centimeter thick insulated walls, triple glazing, exterior shading that cuts down on cooling by 30 percent, and a co-generation plant that will use waste heat from power generation for heating and cooling. Transportation will be provided by low-energy elevators and for those who want to walk (or get exercise) there is a 9650 meters long ramp running from the first to the 170th floor. According to Treehugger, construction is set to begin this June and is expected to be complete within seven months (210 days). The rapid pace of construction and the overall design for such a massive skyscraper could be a cause of concern, but if Broad Sustainable Building pulls it off, it may show the world how sustainable density can be achieved on a massive scale. The company assures that the building will be able to withstand a Magnitude 9 earthquake and will have a three-hour fire resistance rating. Lloyd Alter at Treehugger sums it up well: "This is going to be a controversial vision of sustainability; putting 30 thousand people in a single building is a hard sell. It is not the bucolic version of green living that most people think of. It certainly is a lot higher than what I have called the Goldilocks Density. But it is the logical extension of the Edward Glaeser / David Owen thesis that the way to go green is to go up, reducing the amount of land used per person and the distances people travel." A resident of Sky City will use 1/100th the average land per person as a regular global resident and will use only 2 tons of CO2 compared to 5.5 per capita. Probability that the Broad Sustainable Building Company can afford this unbelievable task is very high. Recall that this is a company which built the 30-story building just in 15 days and a 15-story The ark Hotel - just in 6 days!