Biwako (Japon): Rare find of Edo Period ruins

Mitsuo Ueno

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BiwakoPillars believed to be a part of an Edo Period structure in the bed of Lake Biwako (Provided by Biwako Suichu Kokogaku Kenkyukai)

Archaeologists have discovered late Edo Period (1603-1867) ruins of a suspected shrine in Lake Biwako here.

The Biwako Suichu Kokogaku Kenkyukai (Lake Biwako underwater archaeology research group) at the University of Shiga Prefecture in Hikone announced the rare find on Nov. 4.

This is the first time that pillars of an underwater structure have been found so relatively intact,” said Hiromichi Hayashi, a professor emeritus of archaeology at the university. “It is an epoch-making discovery in the history of underwater archaeology.”

The relics form a hitherto missing section of the Nagahama Castle ruins off the northeastern banks of Biwako, the nation’s largest lake.

Due to their unique structure, the researchers said they think the remains may have been a shrine dedicated to a deity that oversaw the castle or local area.

The architecture likely sank into the lake in subsidence caused by a major earthquake, the archaeologists said, as the ruins are located in waters deeper than those recorded in contemporary documents.

Carbon dating of the pillars and earthquake records show that the building probably descended to the lake floor following a magnitude-7.2 tremor that struck the region in 1819.

The same earthquake is believed to have caused stones of the Naoesengen ruins to sink 4 meters below the surface of Lake Biwako, 250 meters off the city of Maibara, south of Nagahama.

Using scuba gear, the excavation team found eight wooden beams protruding from the lake bed about 100 meters west of the bank at a depth of 1.8 meters.

Six of the beams had a diameter between 17 and 20 centimeters and were 46 to 66 cm in length. Four of them, which are likely pillars, were set up 1.8 meters apart, north to south, and 2.1 meters apart, east to west.

The remaining two are thought to have formed part of the eaves of the structure.

A layer at least 30 cm thick of fist-sized rocks was also found scattered around the pillars over an area with a diameter of about 8 meters.