It's undeniably exciting to hobnob with celebrities and tycoons at this four-story brownstone landmark, a former speakeasy that opened on December 31, 1929. The Grill Room features roomy banquettes and a ceiling hung with toys, and Upstairs at "21" is an intimate 32-seat restaurant with a luscious $85 four-course prix-fixe menu. Thus, chef Erik Blauberg can satisfy everyone, retaining signature dishes like the famous "21" burger and other New American food downstairs, while offering more eclectic fare upstairs, such as cinnamon lavender duck and pistachio mint poached turbot. Service is seamless throughout. Reservations essential. Jacket and tie. Subway: B, D, F, V to 47-50th Sts./Rockefeller Center.