Inside, greeted by staff, then up to the top floor where the control room is situated adjacent to a large display area, the floor of which features a satellite map detailing the path of the system's main tunnel.
The system is designed to prevent flooding of the basin during typhoons and heavy rain events by draining water from four rivers spread across the region. Each of the rivers has a 32 metre diameter, 60-70 metre deep underground shaft into which water can be diverted. These silos are joined 50 metres below the surface by a 6.4 kilometre long, 10 metre diameter tunnel that feeds the final shaft, which in turn connects to one end of the giant pressure control/surge tank. The tank acts as a buffer to regulate the flow of water so that it can be pumped into the Edo River 江戸川 at up to 200 cubic metres per second.