The slanted crown is 160 feet tall, and was originally intended to hold solar power conversion panels.
The tower's base is cut away at the four corners, leaving it standing dramatically on a cross-shaped footing which extends from the core to the center of each side.
Plans for creating residential space on the upper floors were abandoned due to zoning restrictions.
Double-decker elevator cars reduce the area devoted to the vertical circulation core, leaving more space available for offices.
A computer driven load mass damper enables the reduced number of vertical supports and ensures the stability of this building.
The overhanging corners were designed after St. Peter's Lutheran Church, which occupied one corner, insisted on keeping its lot and its separate identity. A new church was however built in place of the old one.
The atrium, open-air concourse and office tower lobby were renovated in 1997.
Citigroup Center was acquired by Boston Properties in 2001.
Standing out among the flat-roofed prisms of midtown, Citigroup's pitched roof has become a powerful symbol of its namesake corporation.