Updated

The Capitol Visitor Center, the largest and most costly construction project in the Capitol's history, will open to the public on Dec. 2, congressional leaders said Thursday.

The opening would come eight years after ground was broken on the three-story underground complex on the east side of the Capitol between the Capitol building and the Supreme Court. Final costs were recently estimated at $621 million, more than double the $265 million anticipated when the project began.

House Speaker Nancy Pelosi, Senate Majority Leader Harry Reid, Senate Republican Leader Mitch McConnell and House Republican Leader John Boehner said the official public opening would come on the 145th anniversary of the completion of the Capitol dome — Dec. 2, 1863 — when the Statute of Freedom was placed atop what was then the new dome.

The 580,000-square foot visitor center features two large orientation movie theaters and an exhibition hall with documents and artifacts from the National Archives and the Library of Congress. It will also boast a 550-seat cafeteria, gift shops and other amenities for visitors who now must wait in line outdoors for tours of the Capitol.

The project was originally scheduled to be completed in January, 2005, but the date was pushed back several times after the Sept. 11 terrorist attacks, as lawmakers decided to add security components to the center, including emergency evacuation routes. They also expanded the project to include more work space and meeting rooms.

Workers have also planted nearly 100 trees and restored fountains, lanterns and seat walls on the plaza above the center, to revitalize the park-like setting designed in 1874 by Frederick Law Olmstead.