Koen-Dori Classics is a small performance space located underneath a church in the heart of Shibuya. It seats maybe 30 people max, with all seats facing the performance area (there's no stage).
The lineup of events leans towards the experimental; fans of improvisational music and dance will love this place. It's a unique spot right in the heart of commercial Shibuya madeness. There's performances almost nightly but check the website for details; the space is available for private rental so if you have an event you'd like to hold this could be a great spot for it.