The Drake Underground, as the name would suggest, is the basement level of the Drake Hotel.
It normally hosts concerts and DJs spinning particular styles of music. I think that it's a great venue for an intimate dance night.
One of the cool things about the Drake is that it's usually a flat cover charge for all levels, so you can wander around between the floors. If the Underground is empty, you can hang out on the main floor. If you meet someone on the main floor, you can take them downstairs to hang out too. It's more fun than a one room venue.
The Drake Underground has a great sound system, with no need for ear plugs. It's dark, and when the dancefloor gets packed it can be kind of hectic (in a good way!). The relative darkness is a great environment for dancing.
There are always couches on the side, so you don't really need coatcheck either. I love how laid back it is.