Codfish Hollow is great! Saw Wilderado there a couple years ago. Such a different experience... but awesome! It is in a really cool barn, but they leave the one end nearly entirely open.You’re right, I always thought it was an outdoor venue but looks like it is in a barn.

There's usually plenty of room inside the barn for everyone that wants to be in there, but some people just hang out outside, relax on the hillside, and just listen to the music from there.
Inside...
