“A seed, given water and light, extends its roots, grows leaves and comes into flower. It spreads its roots in search of soft soil and places its leaves so they receive as much sunlight as possible.” The Iidabashi subway station is very much an architectural version of this statement. Watanabe starts 35 meters underground with the “roots” – the tubes of the station, and as they extend up they create a wing” or “flower” which is the ventilation tower for the station.
The exposed structure of the station was one issue of design that Watanabe wanted to hold strong to, as it was part of making the invisible visible. The tunnel-ways of the station are composed of three cylindrical tubes, joined together. The two outer ones are for railways and the center is for the station and access ways of passengers. When exposing structure there is always the issue of waterproofing and such, which Watanabe solves by such: by placing slabs in both adjacent tunnels of the station where ducts could be installed, the need of a duct over the station tunnel could be eliminated. The remaining space under the station platform was used for a pit where pipes and wiring could be strung. Gutters for waterproofing fitted beneath overhead beams, collecting water and directed it through pipes through supporting columns.