After 13 years, 1 World Trade Center is open again for business.

Condé Nast, one of the anchor companies of new 1 World Trade Center, moved in its first 175 employees to the new offices on Monday.

"The New York City skyline is whole again, as One World Trade Center takes its place in lower Manhattan," Port Authority executive director Patrick Foye told The Associated Press. The Port Authority owns both 1 World Trade Center and the site.

The 1,776-feet high tower is the tallest building in the Western Hemisphere.

About 175 of the 3,000 expected employees moved in Monday.  The rest are to arrive by early 2015.

More than 2,600 people died when Twin Towers fell on Sept. 11, 2001.