Pipe socket
Fig. 23: Did another pipe once lead into the depths here or is this meant for future higher water pumping? Dive 661: Dive site Rüschlikon pumping station, Lake Zurich. Nikon D200; Δt=1/80 s; f=10.5 mm; f/4.0; ISO 100; 14 June 2019 10:04:21