To minimize screening time, all equipment and gear are left inside the compound. After a learning curve, crews started to "go through the line like frequent airport travelers," says Champion.

Occasionally, bomb-sniffing dogs are brought in, especially to check deliveries. There have been no breaches to security during construction, Champion adds.

The Secretariat was reoccupied last year, within three months of the original 2007 time estimate. The conference-building restoration, delayed mostly by the security redesign, wraps on April 1.

In May, the year-long, $100-million restoration of the General Assembly Building is scheduled to get under way. It is the last major piece of the project.

The U.N. already is planning its next big undertaking: the renovation of its Geneva headquarters. "They've already picked our brains about lessons learned," says Champion, who advised the Geneva planners to gather the CMP, the construction manager and the design firms earlier in the project. "An expanded preconstruction phase would have helped."