What is the history of the structure for the twin towers?

Answer:n the depths of the emotional underworld at Ground Zero, an eerie place of crushed fire engines on plinths and dramatically lit scorched steel columns, is a fascinating site of architectural archaeology.

Marching in a mute line around the exhibition halls of the 9/11 Memorial Museum stand the original foundation pads of New York's iconic "twin towers", their rusted steel plates still bolted firmly into the Manhattan bedrock. Across the hall, a grid of massive steel bolts emerges from the 20-metre-high slurry wall, the vast concrete barrier that was cast to keep out the waters of the Hudson River and which held firm when the towers collapsed on 11 September 2001, stopping the subway tunnels beneath from flooding.

Along with a few charred columns which loom like devil's forks above the entrance to the museum, this is all that exists of the original World Trade Center. But perhaps even more so in their absence, the twin towers remain one of the most powerful symbols of New York City.