Architecture and stage sets are David Rockwell's métiers. Combining them, taking essential elements from each in a kind of alchemy, is his imprimatur. And that's evident the moment you pass beneath the theater-style glass marquee of New York's Carlton Hotel on Madison Avenue, then through the revolving door. The man behind Broadway sets for The Rocky Horror Show and Hairspray, Rockwell used curtains, scrims, scaffolding, and, of course, spotlights throughout phase one of his Carlton renovation: building a 17,000-square-foot three-story annex, which now houses a new lobby and meeting rooms, and designing a 7,000-square-foot duplex restaurant for star chef Geoffrey Zakarian, next door in the original beaux arts hotel.

"The old building was the main attraction, so we needed to integrate it with the annex," he explains. "We had to discover the old building's unique DNA and use it to tie the two together." Unearthing mosaic tile floors and elaborate egg-and-dart molding during the renovation helped the Rockwell Group produce that seamlessness. The result is genuine synergy. As you move from lobby to restaurant, new and old are often difficult to tell apart. The historical gets woven with the contemporary for a "feel of something that evolved over time," Rockwell says.

It's equally difficult to draw the line between performer and audience, stage sets and box seats. As the triple-height lobby and the restaurant were designed to open to each other, hotel guests arriving down the curving stairs can look up and see diners on the balcony of the second-floor main dining room. For diners looking down on hotel guests checking in, it's the same voyeuristic thrill in reverse.

Adding to the human drama in the lobby, Rockwell designed a multilayered focal wall built around a 24-foot-high black-and-white archival photograph of the original hotel-the facade's terra-cotta details and bands of brick anchoring a stretch of Madison Avenue. He backlit the image, which is printed on a scrim, and covered it with a sheet of textured glass; water flows down the glass into a limestone trough where Rockwell placed polished river rocks and a row of up-lights. Above the waterfall, stenciled panels look like café au lait damask. A pair of columns wrapped in gray faux suede complete the composition.

Guests lounging on the lobby's sofas and wing chairs can contemplate the waterfall or turn the opposite way for a glimpse of Rockwell's most dazzling discovery, the stained-glass dome above the restaurant's main dining room. With colored pieces now attributed to Louis Comfort Tiffany and other parts to a turn-of-the-last century Indiana glassmaker, the 200-square-foot dome was hidden for years by a dropped ceiling, and much of the glass in the pattern of grapes and trellises was shattered or missing. "Uncovering this really fantastic skylight was one of my favorite moments, definitely a pinnacle of the design process," recalls Rockwell, who also learned while delving into the building's history that the dome had once topped a gentlemen's barroom. "It took more than eight months to remove the layers of tobacco tar and dirt. They were so thick that, initially, it looked like black paint."

As an ensemble, the main dining room and the café beneath have a name that suggests a more casual establishment than Rockwell's first restaurant design for Zakarian: That one, uptown at the Chambers hotel, is called Town; this one is Country. Still, Country's main dining room is naturally more formal than the café, a difference reflected most vividly in the lighting. Above the white cloths of tables in the dining room, pendant fixtures' frosted-acrylic boxes encase sparkling period-style crystal chandeliers. (This juxtaposition of traditional and contemporary picks up on a treatment in the lobby, where old-fashioned crystal chandeliers hang inside cylindrical stainless-steel mesh shades.) Down in the café, the layered approach reappears, but this time it's fabric-wrapped cubes in clear acrylic boxes that cast their light on marble or walnut tabletops, Harry Bertoia's bar stools, and oak flooring wire-brushed in an overscale herringbone pattern. Over the bar, a translucent acrylic shelf glows like a light box, silhouetting the bottles inside. "I'm taking a romantic look forward to what hotels and public space in general can become," Rockwell says. "There's no defined period. You can breathe your own fantasy into it."