"Housed in the ground floor of the opulent Riggs hotel, Penn Quarter’s Café Riggs serves a robust all-day menu in an elegant European environment. The nitro espresso martini ($20) is served on tap using espresso, Ketel One vodka, and Mr. Black coffee liquor. On “Martini Monday,” they’re priced at $16 each." - Tierney Plumb, Emily Venezky, Mekita Rivas