From WSDG:

What it sounds like inside a nuclear power plants cooling tower.
Matt Ballos and Kevin Peterson of WSDG were out in Elma, Washington this week to visit NWAA acoustic test labs. The lab is built in a nuclear power plant that was abandoned a few weeks before it received its first uranium.

In between the acoustic lab parts of the trip they were able to go around and explore the rest of the abandoned facility. This video is in one of the cooling towers. Even though it has an open top it does have a convex curve on the inside bottom of the tower. This shape makes for some awesome acoustics as you hear in the video.

[WSDG (Walters-Storyk Design Group) | Via BoingBoing]