There are a number of flak towers dating back to World War II left in Vienna. Their interior is usually not open to the public. The »78er — Institut für Stadterkundung Wien« entered at least one of those towers to bring us back some pictures.
The functional, depressing, and partly derelict architecture of towers is a harsh contrast to the panoramas from their tops and their immediate surroundings. I highly doubt it but I wonder if the signage in there is original.