FOSTER Maki Rogers,” it says on the doors leading to an 11th-floor design studio overlooking ground zero.

No such high-powered international architectural partnership actually exists. But Norman Foster, Fumihiko Maki and Richard Rogers all have employees working together in an unusual collaborative office as the second, third and fourth towers of the new World Trade Center take shape.

Tower 1, the Freedom Tower, was born in a flurry of headlines as its architect battled ground zero’s master planner, then had to return to the drawing board after the police questioned the building’s security.

Tower 2, designed by Mr. Foster, has already generated controversy, since it will displace what is called the survivors’ stairway on Vesey Street, the only aboveground remnant of the original trade center still standing where it did on 9/11.

But except for that, the towers have largely been out of public sight since the first renderings and models were unveiled last September by the developer, Larry A. Silverstein