After Stephen Colbert came twirling onto his new stage for the first episode of “The Late Show” on Tuesday, he thanked his adoring crowd, then looked straight up to the ceiling of the Ed Sullivan Theater.

Later, when his guests, George Clooney and Jeb Bush, appeared on the set, they, too, craned their necks to get a good look at it.

And what was up there?

“Tonight is the first time anyone has seen a renovated Ed Sullivan Theater, and look at that incredible dome up there, look at that,” Mr. Colbert said early in the show, as a camera swept upward to reveal the domed ceiling, with the CBS eye logo and the new host’s face playfully displayed in kaleidoscopic rings. “That is all digital projection. I wanted to have Michelangelo paint it, but it turns out Ninja Turtles aren’t real.”

The images were a projection, but that dome, and the chandelier within it, were very real. CBS knocked down the light fixtures, sound barriers and an air-conditioning duct that concealed the ceiling when David Letterman was host, bringing it back to something resembling its original 1927 state. The dome, along with restored stained glass on the perimeter of the theater, allows the evocative fixtures of an old Broadway show house to merge with the modern accouterments that were added for Mr. Colbert’s show: a new marquee and a high-tech set, featuring LED lights and video walls behind his desk.