Muru Pops Down, a project that's part of World Design Capital Helsinki 2012, is a pop-up restaurant that literally takes place underground: 262 feet underground, to be exact. Running for two weeks between September 10 and 24, Muru Pops Down is an offshoot of Helsinki restaurant Muru.
The dinner takes place in the Tytyri Mine Museum, and diners are given helmets to wear as they navigate the mines to the restaurant. (They don't have to wear the helmets while they eat, though.) The dinner costs €128 (US$161) and includes transportation to and from Helsinki to the event, dinner, drinks, and museum admission. Alas, would be gastronomic spelunkers, it's sold out.