Friends from out of town often have the best suggestions about what to do in your own city.

My friend Dan blew into town playing tuba with the What Cheer? brass band from Providence last week. He and the baritone player had heard about Teufelsberg, an abandoned US sonic spying station, tucked away in the Grunewald, a beautiful stretch of parks and suburbs on the outer edges of Berlin.

Dan heard that the abandoned complex was topped by geodesic domes with amazing acoustics, so we brought instruments and recording devices.

The listening station sits atop Teufelsberg which means Devil’s Mountain. The hill was built out of 12 cubic meters of rubble from World War II, including a Nazi military technical college. As we walked around the wooded trails in the Grunewald we wondered where the place could possibly be. Then we caught a glimpse of a white balloon.

We shimmied through a hole in the fence and climbed up a rain slicked hill to check out the remains of the complex. Old wires, glass, and broken equipment was everywhere. The complex had some of the best graffiti that I’ve seen in Berlin. I’ve heard from friends that depending on when you go it’s either full of families or seedy characters. Unfortunately, we had the latter, but I’ve talked to enough people who have visited repeatedly to assure anyone that wants to go that it’s safe!