The Underground (more commonly referred to just as "the nightclub") is a bar/club with a large stage that caters to the Avalon's many bands. In is owned and operated by Tim and Abbie Okypete.
Samuel Ainesborough works their as Tim's apprentice and waiter.
The club has a least two levels, the first is the main area and already below ground, the second is a basement level.
Currently Tim and Sam are currently constructing an Tunnel that bypasses the L.A entrance with the hope that more open minded humans like Tim will come to the nightclub. The tunnel entrance is near a shop called "Ravi's house of eastern curiosities"
While Jim Finn insisted his farewell do be held her his parents do not trust the place, believing it is run by some "shady indivduals".
The Boney Kings of Nowhere are seen hanging out here during the Exchanges Arcs, despite Tim's attempts to stop people hanging out at the club all hours of the day.