By then, Philadelphia was a much changed place. Jobs and people were leaving for the suburbs, and a new, progressive administration was struggling to modernize the city’s neglected infrastructure. At Penn, the design faculty was undertaking their own reckoning, as they reflected on modernism’s harsh treatment of older architecture. Geddes joined Kahn, Venturi, Romaldo Giurgola, Denise Scott Brown and others in formulating a more sympathetic approach, which led them to being lumped together as the Philadelphia School. The group’s “architecture was different,” Geddes explained in a history of the period written by Pratt Institute professor John Lobell. “Our buildings were neighbors of buildings that were there before, and that would come after.”

Geddes’ first project, Pender Labs, was a perfect demonstration of that ethos. Designed for Penn’s engineering school in 1958, the four-story cube was squeezed into a small space between two early 20th-century structures. While Pender’s rigorously gridded facade was stylistically distinct, Geddes' use of materials and scale made the trio feel like natural companions. Sadly, Pender was torn down in 2003 to make way for a much larger infill building.

Geddes’ respect for connectivity and city streets didn’t prevent his firm, Geddes, Brecher Qualls Cunningham, from occasionally departing from the grid. In Philadelphia, he is best known for his 1963 police headquarters, a sinuous, double-barrelled, concrete structure with a facade of taut, washboard-ab windows. Geddes, who was deeply committed to collaborations with engineers and planners, tapped August Komendant, who pioneered the use of prestressed concrete (and later worked with Kahn on the Kimbell Art Museum) to develop the structural system. Every window frame had to be individually designed—no mean feat in an era before computer-assisted design. Although the building, nicknamed the ”Roundhouse,” was part of a city effort to professionalize the department, it became linked in the minds of many Philadelphians with the police abuses that took place inside. Since the department moved to new quarters last year, the Roundhouse’s fate has been uncertain.

Geddes, who spent countless hours in conversation with Kahn and other Penn faculty, was as much a teacher as a practitioner. By the mid-’60s, the Philadelphia School was breaking up, as its members achieved success. Geddes left his beloved Philadelphia in 1965 to become dean of Princeton’s School of Architecture, and would spend the next 17 years building up the department. The position gave him the opportunity to design the serene dining hall and Birch Garden Quad at the Institute for Advanced Study, also in Princeton.

While it’s easy to focus on Geddes’ memorable building designs, he also left an important legacy of downtown plans. His work on Philadelphia’s 1988 plan for Center City, and a redevelopment proposal in Princeton, reinforced the value of retaining the existing street plan and creating lively blocks with buildings from many periods. Geddes continued to teach and lecture well into his 90s. In 2013, he finally published a manifesto calling for architecture that was sympathetic to cities. It was titled, appropriately enough, Fit.