You can spend hours at 172 Duane Street, in Tribeca, and still have no clue what's going on here. People come and go at all hours. A thick cloud of pot smoke makes you think you've wandered into a building on fire with a stereo cranked at full blast. Sometimes the four-story warehouse is a sprawling art gallery; at other times, it's a photo studio, or an indie band's rehearsal space. Most of the time, it's all of these things at once.