As if Gilt Bar weren’t gorgeous enough, there’s an even more intimate speakeasy called the Library hidden below it. Red velvet tufted banquettes, antique leather-bound tomes, and exposed brick create a romantic ambience in this dimly lit subterranean bar. In addition to specialty cocktails, the Library serves the same menu as Gilt Bar upstairs. 230 West Kinzie Street; giltbarchicago.com
Situated in a building near the Pacific Ocean in Venice, California, the Del Monte Speakeasy has been serving booze (legally or illegally, depending on the year) since 1915. During the Prohibition era, the bar (which is still underground) was located below a grocery store.