Mr Silverstein also complained that the slurry wall, which was to remain exposed, was simply ugly.

BBC: The battle over Ground Zero

Today, the Slurry Wall is one of the most haunting features of the World Trade Center Memorial Museum.

FORBES: The Bathtub. Lower Manhattan's Wall Against Water.

Make concealment and revelation work together symbolically, with the slurry wall as witness.

WSJ: Daniel Libeskind Envisions Ground Zero

The bathtub was the 9-block area of the World Trade Center site at bedrock, that was protected by the slurry wall.

FORBES: The Bathtub. Lower Manhattan's Wall Against Water.

There is serious cause for alarm, however, in the treatment of the slurry wall in the revised version of the plan.

WSJ: Daniel Libeskind Envisions Ground Zero

As visitors descend underground into the museum, they'll see the slurry wall, the bedrock that held back the Hudson River when the towers collapsed.

CNN: Creating 9/11 memorials a slow process

Paul Gray, 50, disappeared when he climbed over a wall and into the pit after Craig Whipps became submerged in the slurry at Albyns Farm, near Ongar.

BBC: Essex farm workers 'overcome by slurry'