Thanks for asking!
An ice bar is kept at around 28 degrees. The bar, walls, glasses, and benches are made of ice, and all they serve (as far as the ones I'm familiar with) is vodka (in a plethora of flavors and fruit juice mixes). There are a few around the world and gaining in popularity.
The number of people at one time is limited, so sometimes there can be quite a wait to get in. The ice bar provides the insulated ponchos and gloves (and boots, if I recall correctly). It's really fun and different, but no one spends more than 30 minutes to an hour tops.
I hear that one of the cruise lines (Norwegian, maybe?) is planning an ice bar on their newest ship--that'll be a "hot" spot for sure!