It was all the fault of the glass flooring. When Paris department store La Samaritaine was first built, at the turn of the 20th century, electric lighting was in its infancy: to increase illumination, every level, from the atrium’s summit to the three-floor basement, was paved with translucent Saint-Gobain glass block—1 million square feet of it—set into metal T joints. Covered up and forgotten in later decades, it would prove the building’s undoing. In 2005, the authorities deemed the flooring a safety hazard—the T joints, they said, would buckle in a fire—and closed the store overnight. In the aftermath of the debacle, La Samaritaine’s owner, luxury giant LVMH, drew up an $890 million redevelopment plan. Where once the Samar’, as it was affectionately known, had sold everything imaginable to anyone who walked through the door, it would now cater exclusively to wealthy tourists: 215,278 square feet of shopping mall peddling high-end brands—a 26-room,46-suite five-star hotel—as well as 161,459 square feet of commercial office space. In return for rubberstamping this giant gentrification job, the City demanded, and got, 96 social-sector apartments and a daycare center.