New World Trade Center climbs to 100 stories

-- The new World Trade Center has reached a milestone. The skyscraper being built to replace the terror-wrecked twin towers has reached 100 stories.

That's just four floors short of One World Trade Center becoming the tallest building in New York City.

There's a special twist when it comes to counting floors.

According to the Port Authority of New York and New Jersey, the tower grew by a half dozen stores overnight, from 94 last week to 100.

That's because those floors don't actually exist. The numbers were skipped to make up for the building's massive base, plus mechanical equipment taking up space.

Condé Nast has signed a tentative agreement to move into the tower. It is expected to open next year at the northwest corner of the 16-acre site.