The owner of Mercury Café calls it a community center. The cafe exudes a vague hippie aura and serves as a restaurant, bakery, coffeehouse, dance club and concert hall. It is hard to pinpoint the exact style of this eclectic nightspot, serving up everything from Celtic and Cajun to theater and poetry. Swing and salsa bands are regulars on the second floor, which accommodates 350. The main dining room might feature a concert pianist one evening and a string quartet the next. The dinner menu offers salads, sandwiches, pasta dishes and steak.