long underground round concrete tunnel with a pipe, lit by incandescent lamps. underground tunnel of a heating main or a water

abandoned collector communication concrete dark dirty district heating drainage draining duct ducting ductwork engineering environment exploration gas heat homeless industrial inside interior light line long network people old perspective pipe pipeline pipelines pipes round rusty service sewage sewer subway technical tube tubing tunnel tunneler tunnels underground utility wall wastewater water lit incandescent lamps main supply system lamps system