Marcus Samuelsson’s restaurant at MGM National Harbor debuted last month, bringing the New York-based chef’s comfort cuisine to the splashy Las Vegas-style resort on the Potomac.

Tucked in the back is a music-fueled bar called Sammy’s — named after Rat Pack icon Sammy Davis Jr.  — featuring jazz, DJs and gospel brunches.

Sammy’s is one of the many surprises awaiting adventurous local diners and drinkers who favor establishments featuring specialty bars within bars or exclusive restaurants within restaurants.

The D.C. area has a handful of both, with more on the way.

Amaro lovers can currently take refuge in the six-seat bar dedicated to the Italian liqueur at RPM Italian, while seafood lovers are welcome to feast on crudo at Conosci, the 30-seat counter folded within Alta Strada. The Dabney is developing a basement wine bar, while Eighteenth Street Lounge is putting the finishing touches on a craft cocktail lounge called Addendum. And the Sugar Shack coming to Shaw is expected to house a speakeasy, similar to Captain Gregory’s in Alexandria, Va.

Here’s a look at the Russian nesting dolls of the hospitality world operating in the immediate area.

RPM Italian

Bill and Giuliana Rancic’s RPM Italian offers a six-seat amaro bar that features more than 13 types of the bitter Italian herbal liqueur.