Cumberland Caverns in Tennessee is home one of the most unlikely concert venues you'd ever expect. The venue is nicknamed the Volcano Room can hold 600 people and is 333 ft. below the surface.
The acoustics of the room are interesting to say the least. The house engineer says that the venue doesn't really create much of an echo like you would expect. He attributes this to the uneven surface of the walls of the cave.
The temperature of the cave remains at 57 degrees F all year long. People have been known to take blankets down in the middle of the summer.
Finally, one negative of the venue being in a cave is that the humidity is extremely high. The high humidity can be troublesome for keeping instruments in tune.