The World Trade Center was destroyed by terrorist attacks on September 11, 2001. The WTC was a complex of 7 buildings in Lower Manhattan of which the Twin Towers were best known. The two towers were different in height, the first one, built in 1972 being 417 meters and the second one, finished on year later measured 415 meters. The One World Trade Center was the highest building in the world until 1974, when the Sears Tower was built in Chicao. When destroyed, the Twin Towers still ranked in the top 10 of the highest buildings in the world and dominated the skyline of lower Manhattan.

The World Trade center was a project started up in 1960 by David Rockefeller. The towers were sometimes nicknamed David and Nelson, the Rockefeller brothers. The design came from Minoru Yamasaki and Emery Roth & Sons. The monolithic Twin Towers were never seen as great architecture, but it certainly was a great engineering feat.

The Building never received the attention the Empire State Building gets. But it first became world news when, on friday Feb. 23, 1993 at 12:18, a bomb exploded in the World Trade Center. The explosion, destroying 5 floors in the 110 story building, including the central commando center, trapped about 50,000 people, killed 6 and wounded at least 1000 people. Moslem fundamentalist have been convicted for the bombing.

The second time the WTC became world news was on the tragic day September 11, 2001 when 2 hijacked planes crashed into the twin towers. Not much later, the towers imploded. More than 2,800 people died in the terrorist attack.

Even though the towers were built to withstand the impact of a plane crash, the towers collapsed within 2 hours of the initial impact. But an investigation into the cause of the collapse of the towers found no structural flaws or blunders. Some of the reasons of the collapse are:

- the size of the planes: the Boeings that crashed into the towers had a wing span of 156 ft, while the towers were 'only' 209ft wide. The planes knocked out so many columns in the building that the remaining columns could no longer support the upper floors.

- the height of the impact: the planes crashed at altitudes were it was almost impossible for firemen to contain the fires. The internal sprinkler sytem was ineffective if working at all, as several floors were wiped out. The amount of kerosine intensified the fires to such an extent that the steel eventually weakened and could no longer support the top floors.

- The structure: after the upper floors collapsed, this caused a domino effect as the floors below could not support the collapsing top floors. This caused the whole building to implode.

The implosion of the towers covered almost all of Lower Manhattan in a dust cloud. Several days later, streets around the WTC, also known as 'ground zero' were still covered with dust. Many buildings in the neighborhood of the attacked towers were either severely damaged or collapsed. Among them One Liberty plaza and the World Financial Center buildings. It took until May 30, 2002 before ground zero was officially cleared: 1,8 million tons of rubble were removed in the process.

Time will tell if this tragedy becomes the Hindenburg of the skyscrapers. The WTC 1 & 2 itself will not be rebuilt, at least not as tall. Several projects for world's tallest or 1000ft+ skyscrapers have already been put on hold or have been scaled down.

Timeline of the WTC attack:

At 8:45 AM EDT, a hijacked Boeing 767, American Airlines Flight 11 from Boston en route to Los Angeles hits the north tower.

At 9:03 AM, a second hijacked Boeing 767, United Airlines flight 175 from Boston en route to LA hits the south tower.

At 9:50 AM, the top floors of the south tower collapse. The whole tower collapses

At 10:28 AM, the top floors of the north tower implode, bringing the rest of the building down.