rohrpost easter

Over Easter my husband and I went to Berlin, home of one of the largest pneumatic dispatch systems (rohrpost) in the world. We found evidence of this history in the Museum für Kommunikation Berlin, a rather quirky place, with a dark little basement crypt dedicated to their treasures, including the capsules below (with more photographs soon).

I looked everywhere for evidence of the old system on the streets or in buildings but could not find it. Does anyone know were to find reminants of the old postal pneumatic tube systems in Berlin, Paris or any other city? Perhaps we could have found some signs if we had taken a tour run by the Berliner Unterwelten E.V: Society for exploration and documentation of subterranean architecture ...