A viewing platform built to give the public a better look at the World Trade Center site opened Sunday.

The line to walk up a long wooden walkway to the 13-foot-high platform stretched around two city blocks — despite subfreezing temperatures — when it opened at 9 a.m.

The rectangular, fenced-in structure at Fulton and Church streets in lower Manhattan, about a block from where the twin towers stood, can hold 400 people.

From it, viewers can see the devastation, including the huge red cranes that have been ever-present since the Sept. 11 terror attacks, and hear the constant rumble of heavy machinery.

"What struck me was the open wide space, no buildings, but it also looks like a construction site," said Scott Smith, who drove to New York from West Hartford, Conn., with his 7-year-old daughter Lane.

"I wanted to see the falling buildings. I thought it would be interesting," said Lane, who was sitting atop her father's shoulders.

Frederic Hustache, visiting from Paris, got up at 6 a.m. to join the line for the platform.

"The point is not to actually see everything. It's to feel what is here," he said.

Mayor Rudolph Giuliani officially opened the platform Saturday, urging Americans to "come here and say a little prayer and reflect on the whole history of America."

Three other platforms are planned, but there was no word on when they would be finished.