What is the surface of XXX made of?
Telecommunication Tower of US-Forces Heidelberg
Telecommunication Tower of US-Forces Heidelberg is an 80 metre tall telecommunication tower of the US Army in Europe on the mountain Königsstuhl which is part of the City of Heidelberg at 49°24′8``N 8°43′59''E. The Telecommunication Tower of US-Army in Europe is one of the few military communication towers built of reinforced concrete and it was built in the late 1950s.
concrete