Akiyoshidō

Akiyoshidō is the great cave of the Akiyoshi plateau in Yamaguchi Prefecture, and the plateau is the point: 130 square kilometres of karst topography holding over 400 limestone caves.

The area became Akiyoshidai Quasi-National Park on 1 November 1955 and covers 45.02 square kilometres. Like all Japanese Quasi-National Parks it is managed by the prefectural government rather than the national one, and it is rated a protected landscape, IUCN category V.

The water underneath is recognised in its own right. The Akiyoshidai Groundwater System is a Ramsar Site, a wetland of international importance, which is an unusual designation for something you cannot see from the surface and a good indication of how much water moves through this rock.

The park is properly equipped: a natural history museum, a visitor centre, a rest house, a youth hostel and a park headquarters, with a scenic roadway across the plateau and several walking trails.

Its calendar says a lot about how the landscape is kept. There is a fireworks festival in July and a Karst Walk in November, and every year the plateau grassland is deliberately burned off. That burn has a name, Yamayaki, and it happens in February. It is not decoration: as farming took hold, local people replaced the forest that once covered this ground with Japanese pampas grass for animal feed and for thatching, and burning is how that grassland is kept.

Above ground the plateau is a field of pale rock teeth standing out of grass. Below it, Akiyoshidō runs on for kilometres, and the lit tourist section is a fraction of what has been surveyed.

The rock is uplifted Paleozoic reef limestone, thickened by overfolding during the Akiyoshidai orogenic movement, and erosion since has left an undulating karst dimpled with dolines and studded with limestone pinnacles up to two metres high.

The caves beneath have produced Pleistocene fossils from the last interglacial: Japanese rhinoceros, Stegodont and Naumann elephants, tiger and much else. This country was heavily forested about 500,000 years ago. By the Jōmon period it was a hunting ground, with the bottoms of sinkholes used as vegetable plots, and numerous Paleolithic artefacts have been recovered.