Is there any architectural category more reviled than the concrete high-rises built in the 1960s as subsidized housing? Philadelphia, like many American cities, has been systematically obliterating its public-housing towers, which were known as much for their harsh designs as for poverty and crime. And yet one dramatic exception has managed to age with grace amid the leafy, redbrick streets of Washington Square West.

Casa Farnese, the gleaming white International Style tower at 13th and Lombard, is the work of Oscar Stonorov, an important Philadelphia modernist who collaborated with the likes of George Howe and Louis Kahn, and was a devoted follower of Le Corbusier. He completed the 18-story residence for low-income seniors in 1966, four years after his upscale Hopkinson House on Washington Square.

Casa Farnese adheres to Corbusier's form-follows-function philosophy, yet is full of small, humanizing details. All 288 apartments have terraces, and the service cores that bookend the main slab have an appealing corduroy texture that enlivens the concrete. Stonorov also gave the entrance a big architectural hug, a C-shaped overhang that serves as a counterpoint to the tower's disciplined straight lines.

Once inside, however, you were squeezed into a tiny lobby with barely enough space for a table. As time went on, and security became more of a concern, the lack of a proper reception desk weighed on Casa Farnese's nonprofit owners. So when PRD Management undertook a major renovation in 2012, it proposed to remedy the situation by replacing the overhang with a full-size lobby.

That alarmed preservationists, who feared losing a key design feature. The two sides eventually came up with an ingenious compromise: They decided to convert the overhang into a lobby by completing the circle and adding walls.

The result is a sleek, one-story pavilion that resembles a transparent hatbox. Roomy enough for a reception desk and seating, the new lobby preserves Stonorov's overhang, which peaks out like a fedora brim from the curving glass walls. The structure (by architects Ron Fall, Stacey Jacovini, and Cecil Baker) also does a better job of defining the edge of the shady garden where residents like to sit.

The 1966 tower was the brainchild of Andrew Farnese, a lawyer and civic leader (and grandfather of state Sen. Larry Farnese), and is notable for being the first senior-housing tower in Pennsylvania financed with a HUD grant. A baby boomer now approaching the big 5-0, it has not only survived the backlash against affordable housing, but it serves as a model for how to make such buildings look fresh again.