It's the bass player's private studio. I've been engineering there since around 1996. It's big enough to host live studio performances with an audience of up to about twenty people.
Check out their renditions of Steely Dan. There's some really good playing on it. There's also a documentary on their page about the LLB, and how they got the idea and how they do their videos. its down at the bottom of their page.
We had one 2.5 hour recording session that included warming up and doing multiple takes of three songs until we got takes we were happy with. I probably put in an hour or two on audio mixing this song, then an hour of loading files (for the whole session, not just this one song) into the editor and syncing them up, then another half hour of color matching, maybe a half hour of video editing per song.