The Tamori Club late-night variety show recently took a boat cruise through a system of drainage tunnels beneath central Tokyo.

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Here are a few highlights of the trip.

1:00 - The boat approaches the tunnel entrance, located on the Kanda River next to Mansei-bashi Bridge near Akihabara. The drainage tunnel -- known as the Ochanomizu Diversion Channel -- runs 1.3 kilometers and rejoins the river upstream near JR Suidobashi station. The tunnel is not designed for boat traffic.

2:10 - Tamori tests the echo inside the tunnel.

2:25 - The painted numbers indicate the distance in meters from the entrance.

2:35 - The tunnel measures about 8 meters from floor to ceiling. The water level easily reaches the ceiling after a heavy rain.

3:00 - The boat approaches a round section of tunnel dug with a shield machine. This portion of the tunnel is 8.8 meters in diameter and 760 meters long.

3:50 - The passengers view the rails of a ceiling-mounted crane system used during construction. The crane was used to erect a water barrier to keep the construction area dry.

4:00 - The boat passes a floodgate tunnel on the left.

5:00 - The boat passes a sign reading "Eidan Ochanomizu Station." This type of sign was placed in the tunnel during construction to indicate the nearby infrastructure. Due to its proximity to the subway station, this part of the tunnel is built with extra reinforcements.

5:30 - The boat passes a similar sign for Ochanomizu-bashi Bridge.

5:55 - The boat passes a similar sign for Century Tower, a 19-floor office building.

6:00 - A smaller tunnel branches off to the right. The tunnel is too small for a boat, and the guide is not sure where it leads.

6:50 - The round section of tunnel opens up into a large chamber. During construction, this was a vertical shaft used to lower the shield machine underground. The rails of a ceiling-mounted crane system are visible overhead. A ladder leads up to a manhole on the street.

7:50 - The exit comes into view. Another tunnel continues past the exit for another 1.6 kilometers.

8:30 - The boat exits the tunnel and continues up the Kanda River.

9:30 - The boat passes a pipe pumping water out of the leaky Suidobashi subway station (Mita line).

11:00 - The boat enters another tunnel (Suidobashi Diversion Channel No.2), which runs for 500 meters.