Designed by I.M. Pei as part of an effort to reinvest in the Society Hill neighborhood, the Society Hill Towers offered 624 rental units until they were converted to condos in 1979. Though it's no longer a rental building, it's still a Philly landmark.

Designed by Robert Venturi, the Guild house is an early example of postmodern architecture, and is listed on the National Register of Historic Places, even though it's much younger than most buildings on the list. It provides housing for low-income seniors, and was commissioned by a Quaker organization.

Though the Piazza has its share of critics, it is certainly one of Philly's landmark rental buildings. The Piazza, with its interior courtyard and mixed use design is hailed as a successful placemaking endeavor in Northern Liberties. [Photo by Laura Kicey]

Once a grand hotel, The Touraine was built to impress in 1917. Now it's a luxury apartment building with a unique penthouse at the top

Before it was a luxury rental building, The Drake was a luxury hotel. The Art Deco building is stunning but unsubtle: the ornamentation includes images of "dolphins, shells, sailing vessels and globes."

This example of efficient contemporary architecture was built to house 180 Temple students. The building is significant mostly because of its modular efficiency, and because of its eco-friendliness.