Coronet, SE1 6TJ
The Coronet was once a cinema, but has been turned into a nightclub venue, which occasionally puts on live music as well.
The old cinema seating remains, as do the projectors and screen, but they now overlook the main dance floor. There are two other dance areas, each with their own bar. The cinema seating area is sometimes only opened up when the venue is sufficiently full.
It's right next to Elephant & Castle Station (Northern line), as well as many bus stops, although night buses have a tendency to be very full and sometimes refuse to stop, around the 2am peak time.
The outside of the venue has recently (March 2009) been refurbished, but the inside is still gloriously Art Deco. There are two cloakrooms, one of which is reached via the outside smoking area. For a venue with three floors connected by stairs, moving around is remarkably hassle-free.
Security is reasonably thorough: there are metal detectors, and they confiscated an unopened blister-pack of Nurofen (although you're allowed to reclaim it as you leave).
Red Bull is £3, and water £2.