G-CansFree: All time

G-Cans Project is not exactly located in Tokyo, but an hour train-ride away. It can be a fun offbeat half-day trip. The actual official name for G-Cans Project is the Metropolitan Area Outer Underground Discharge Channel. This world’s largest underground flood water diversion infrastructure was built from 1992-2009, costing some $3 billion. Its other stats are equally impressive: 6.4km of tunnels, 50m beneath the surface, 5 silos of 65m in height and 32m in diameter, and with a pump that can handle 200 tons of water. The heart of it all lies in what is known as The Temple. It is a massive tank charting at 25 x 177 x 78 metres and contains 59 massive pillars. The underground temple is free to visit. Guided Japanese language tours are offered from 3 times a day (10am, 1pm, 3pm) from Tuesdays to Fridays, each lasting about an hour and a half. A Japanese speaker must accompany you or your group to translate the guide for safety reason or else you’ll be denied participation. Apply online a month in advance.

Address: 2nd Floor at Ryukyukan reception, 720 Kamikanasaki, Kasukabe city, Saitama 344-0111
Opening hours: Tours run Tue-Fri 10am – 11:30am, 1pm – 2:30pm, 3pm – 4:30pm
Direction: Train Tobu Noda Line to Minami-Sakurai Station, North exit, followed by 40 mins walk or a 7-min taxi ride (1,000 yen)
Phone: +81 48-746-0748
Website: www.ktr.mlit.go.jp/edogawa/gaikaku/english/index.html

Photo credit: Stan Chow (Flickr CC), Victor Nunez Diaz (Flickr CC), Michael Johngrist