A bit of urban archaeology.
On the Heiligenstock, an empy piece of land on top of a hill east of Frankfurt Preungesheim and north of Frankfurt Seckbach are the ruins of a radio transmitter station. It was build in 1926 for Radio Frankfurt and was later used by AFN and Hesse broadcasting. First there was a wooden radio tower, later metal towers. The station was used untill the 1960s, the station was demolished a few years later. Today there is very little left of the transmitter. Only the concrete fondations of the broadcasting towers and some ruins of technical buildings.
Interesting place, I only learned a few weeks that it exists, even thou I live just a few km away.