There is a small tunnel under a railway near a small german village named Bonaforth. The tunnel has a very special atmosphere and a strange resonance to certain frequencies. It is about 35 meters long, 1.5 meters wide and the height changes from about 3 meters at one side to 1,5 meters at the other side.
There are two recordings on the radio aporee map.
For the second recording we used a pair of shotgun microphones: one (right channel) placed at one entrance pointing to the outside forest, the second one (left channel) is placed on the other entrance pointing into the tunnel.