Iwami Tatamigaura

Published: Aug 11, 2026

Updated: Aug 11, 2026

Iwami Tatamigauranatural monumentfossilsHamadageology

Representative image — not a photograph of this location.

In 1872 the Hamada earthquake lifted a section of sea floor about a metre out of the water, and it has stayed there. The result is roughly 49,000 square metres of flat rock shelf at the foot of a 25-metre cliff, ruled by a grid of natural joints so regular that it looks like tatami matting laid out to the sea — which is exactly what the local name for it, senjojiki, describes. It was designated a national natural monument in 1932.

The rock is Miocene sandstone about sixteen million years old and it is full of things: shellfish, driftwood, and whale bone, visible in the cliff face and the shelf itself. Spherical concretions the size of cannonballs sit on the platform. You reach it through a tunnel driven through the headland, which adds a small amount of theatre to what is otherwise a geology lesson you can walk on. Come near low tide — at high water most of the platform is under the sea.

Essential Information

Opening Hours

Open access | Best two hours either side of low tide

Closed: Open year-round | Inaccessible in rough seas

Entrance Fee

Free | Parking ¥200 per day

Best Season

Year-round | Calm days and low tide matter far more than season

Visit Duration

60–90 minutes

Getting There

Access Information

Kokubu-cho, Hamada, on the Karakane coast. From JR Hamada Station take the bus toward Gotsu to the Tatamigaura-guchi stop, then 10–15 minutes on foot. A small car park at the entrance charges ¥200 per day. Free to enter, reached through a tunnel from the shore. Check the tide — much of the platform is submerged at high water.

Insider Guide

Premium

**Check the tide before anything else.** The platform is a raised shelf, not a beach, and at high water there is very little of it above the sea. Two hours either side of low tide is the window, and it makes the difference between a remarkable site and a short look at some rocks. **Look for the fossils and the concretions.** Shell beds, fossilised driftwood and whale bone are in the cliff and the shelf; the round stone balls sitting on the platform are concretions weathered out of the sandstone. There is interpretive signage, but knowing what to look for before you arrive helps. **The tunnel is the way in.** Access is through a tunnel bored through the headland, and it is unlit in places. It is short, but a phone torch is worth having. **Wear grip.** The surface is wet rock with weed on it and shallow pools between the joints. It is flat, so it is not difficult walking, but it is slippery. **Pair it with kagura.** Hamada is the centre of Iwami kagura and there are weekly Saturday-night performances in town. Platform in the afternoon at low tide, kagura in the evening, is a strong day in a city almost no foreign visitor stops in.

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