University Apartments (University Park Condominiums)

The commission came near the close of Pei's twelve years with the developer William Zeckendorf, for whom he also designed, in the 1950s, Kips Bay in Manhattan and Society Hill in Philadelphia. He set the two ten-storey twin towers on the median island of 55th Street, in an effort to keep Hyde Park's suburban character while rebuilding the parts of the neighbourhood worst hit by decay. He carried out the project with the Chicago architect Harry Weese, who designed the neighbouring town houses.

The two buildings, 540 units in all, were completed in 1961. Designed as rentals, they became condominiums in 1978. When they joined the US National Register of Historic Places in 2005, the file credited the design to the firm Loewenberg and Loewenberg and to I. M. Pei; Pei had a letter from his assistant state that he did design the project, helped on the design by Araldo Cossutta, formerly his partner.

The two identical ten-storey concrete towers are in the International Style. They stand on either side of a central garden with a fountain and are joined to each other by an underground garage. They rest on rectangular pillars more than a storey and a half high, set on a platform raised about two feet (about 60 cm) above the streets. The pillars give a sense of openness, light and space: from every surrounding street, passers-by can see through the garden to the streets opposite. Each tower holds 270 apartments.

The outer wall is a load-bearing concrete screen, worked out by Pei's staff with the engineer August F. Kommendant. It is broken into a great many slender columns and shallow spandrel beams, each neighbouring pair forming the supporting frame for one window, set in arched openings that run nearly floor to ceiling. Fibreglass forms were used to cast the concrete in place, an early and inventive use for structures of this kind. The lightweight concrete stood in sharp contrast with the buff brick of the neighbouring town houses. Seen from east or west, the buildings look like two narrow towers astride 55th Street; viewed at an angle from afar, their vertical lines make them seem shorter than their 469-foot length (about 143 m).

Pei here takes up Le Corbusier's notion of city housing set in parkland, which allows a tolerable density without the strain of monumental construction.

The two buildings, residential condominiums, can be seen from the surrounding streets, astride 55th Street in Hyde Park.