Back in January, the muralists arrived, tiptoeing into the Pierre Hotel in Manhattan at midnight. They erected scaffolding in the grand oval space known as the Rotunda Room, climbed up and stretched out on their backs, daubing at the painted clouds that have long drifted across the sky-blue ceiling.

Then, in June, they turned their attention to the shiny faux-marbling on the stair railing (so dated), applying a subtler matte finish. And earlier this month, under the direction of the architect and decorator Daniel Romualdez, a squad of skilled workers appeared: Electricians installed theatrical lighting to highlight the room’s signature feature, its fantastical wall mural; floor contractors polished the parquet; and new furniture was carried in.

All these efforts — the results of which were unveiled July 12 — have resurrected one of New York’s most spectacular gathering spaces. Beloved by brides who have taken their vows in the fairy-tale setting, remembered wistfully by those who once partook of its formal afternoon tea, and long familiar to members of the city’s upper crust who have mingled here during debutante balls and charity events, the Rotunda Room had languished in recent years. But as new boutique hotels turn lobbies and lounges into hip hangouts, the 86-year-old Pierre is capitalizing on one of its own extraordinary, but previously underused, common areas. And not just for the benefit of travelers who check into the Pierre’s 189 guest rooms and the occupants of its 75 full-time residences, but anyone who needs a place to recover from a shopping expedition to Bergdorf Goodman — or simply wants to revel in the Rotunda Room’s romantic atmosphere.

“It’s always been the heart of the hotel,” said Francois-Olivier Luiggi, the general manager of the Pierre, which is run by Mumbai-based Taj Hotels Resorts and Palaces. “Now we’re turning it into more of a public space.”