There are few addresses in Philadelphia where architecture and history meet as seamlessly as they do at 245 S 3rd Street. In the late 1950s, the City of Philadelphia handed architect I.M. Pei one of the most consequential urban design commissions in American history: the transformation of a derelict food market at the edge of Society Hill into a new model for city living. Pei, the architect who would later stun Paris with the Louvre Pyramid, reshape the National Mall with the East Building of the National Gallery of Art, and reimagine the Hong Kong skyline with the Bank of China Tower, designed this home. Pei's solution for Society Hill was a masterwork of urban intelligence. He positioned his trio of soaring concrete towers close to the Delaware River, then designed a series of three-story townhouses - planned around private courtyard quadrangles - to create a seamless, unhurried transition from his modernist towers to the colonial row houses of one of America's oldest neighborhoods. The result earned the AIA Honor Award in 1965 and a place in the Museum of Modern Art's landmark exhibition "Modern Architecture, USA" that same year. Architectural historians regard it as one of the defining achievements of postwar American urbanism. Step through the deep-set arched entryway - a signature Pei gesture that frames the threshold as a moment of arrival - and the architecture takes over. Flemish bond brick, laid with the precision Pei demanded of every project, meets interior oak floors and oak casework that have only deepened in warmth over six decades. Blackened steel details punctuate the palette with characteristic modernist restraint. At the top of the home, clerestory windows - a deliberate echo of the gridded concrete facades of the towers above - draw light down through the full height of the house, morning to evening, season to season. And beyond the rear of the home, your own private courtyard: enclosed by brick walls and iron gates, designed to turn away from the city and toward calm - the kind of protected stillness that makes urban living genuinely livable. Just beyond, an assigned parking space positioned directly adjacent to the courtyard offers a rare level of convenience and privacy in this setting. Homes of genuine architectural pedigree are rare at any price. A home designed by a Pritzker Prize laureate, part of a project in the MoMA permanent record, in one of the country's most celebrated historic neighborhoods, is an opportunity that seldom presents itself.