Casa Celina now rises cheerfully, a grayish-white, 16-story beacon, above an asphalt parking lot in the Soundview section of the Bronx.

Designed by Magnusson Architecture and Planning, it’s a handsome new home for low-income seniors, several dozen of them formerly homeless. The Bronx has the highest senior poverty rate in New York. More than 50,000 people entered the lottery for Casa Celina’s 204 apartments.

The building is an infill project: It takes over half of the parking lot at a corner of the sprawling campus for Sotomayor Houses, a 1950s-era New York City Housing Authority development. The houses were renamed some years ago for Justice Sonia Sotomayor, who grew up there. During the last couple of years, other low-income senior housing projects have filled in similar parcels of open space on NYCHA properties.

For decades, infill on NYCHA land was pretty much a no-no. Campuses were designed to be low-density with open space, the midcentury urban planning solution to overcrowded tenement conditions of the early 20th century. But tower-in-the-park-style housing created its own problems. Attitudes have changed.

New York City has lately come around to the virtues of adding subsidized housing to architecturally remodeled public library branch sites. NYCHA is a vastly larger owner of public land than the library system. It retains some 80 million square feet of unused development rights across the city. Even a fraction of that could accommodate thousands of new apartments.