Ryujin Dam, Concrete dam in Ibaraki Prefecture, Japan

Ryujin Dam is a concrete dam on the Ryujin River in Hitachiōta, Ibaraki Prefecture. Its reservoir covers 21 hectares and holds about 3 million cubic meters of water. The dam creates the Ryujin Gorge reservoir, above which the 375-meter Ryujin Grand Suspension Bridge crosses at a height of about 100 meters above the water surface.

The Ryujin Dam was built on the lower Ryujin River in Hitachiōta, impounding a reservoir of about 3 million cubic metres with a catchment of 13.5 square kilometres. The pedestrian Ryujin Grand Suspension Bridge above the lake was completed on 28 April 1994 at a cost of roughly 3.3 billion yen, funded partly by the former Suifu village's hometown revitalisation grant, with politician Seiroku Kajiyama credited with pushing the project through.

The gorge's name comes from a legend that a dragon lived in Kamegafuchi, a deep pool formed from an old waterfall basin near the centre of the valley; locals say its water connects underground with Wanigafuchi in Daigo town. Each April and May the Ryujin Gorge Koinobori Festival strings about 1,000 carp streamers over the dam lake.

The canyon is reached by bus from Hitachiota Station on the Suigun Line, about one hour. A roughly 4 km bicycle and pedestrian path runs from near the Ryujin Grand Suspension Bridge to Kamegafuchi along the dam management road. The bridge is one-way in practice: entry is on the south side, and the north bank has stairs and an exit-only gate, so you cannot cross from the dam lake's north side.

The bridge's main towers are shaped like dragons, a nod to the Ryujin name. Since March 2014 it has hosted bungee jumps, and the bridge appears on Japanese television variety shows. Crossing leads to a carillon on the far bank; a staircase and exit-only gate there descend to the reservoir shore.