The city Tuesday unveiled its new high-tech emergency command center, replacing the one that was destroyed when the World Trade Center towers collapsed on Sept. 11.

The four-story building in Brooklyn, across the East River from Lower Manhattan, is the first permanent home for the Office of Emergency Management since the terrorist attack.

"It's one of those agencies that you hope they don't have a lot to do, but you're awfully glad that they work very hard getting ready in case they do," Mayor Michael Bloomberg said.

The new center features a command desk where police, fire and other operations are monitored and coordinated, a 15-foot video wall, and work stations that would enable city, state and federal officials to work together during a crisis. It also has backup generators and enough food and water to last several days.

Hours after the Trade Center towers fell, a nearby 47-story building that was hit by flaming debris also collapsed, destroying the emergency command center that was commonly referred to as "the bunker" even though it was on the 23rd floor.

Temporary emergency centers were later set up where the Office of Emergency Management managed citywide emergencies, including several snowstorms, the 2003 blackout and last year's subway and bus strike.

The city has another emergency operations center at an undisclosed location in case the center unveiled Tuesday is damaged by a disaster or attack.