Vocal Booth and other areas.
As well as a huge live room DARC also has isolation areas for those critical over dubs.
Iso Room A is a medium size live room (7x13) that we use for overdubs and it's great if we need to get a tighter drum sound. The room also divides in half with a few baffles to become a dead 7x7 vocal booth. When it's set up that way we use it as our main vocal booth.
Iso Room B is a small dead iso room (7x5) that we also use for vocals and things like bass guitar.
We also have a couple of great hallways that make really cool echo chambers. This is the old school way of getting crazy 'verb sounds. Just a mic and a sound source in a cavernous hallway. It's simple and it sounds great.
Oh yeah, and one other important feature not to be overlooked. Clean bathrooms!