1530-5 Honjo Oaza Onagara, Saiki, 〒876-0215 Oita.
|L=1,750 m, T=15 °C.
|self guided, L=330 m.
|Onagara Limestone Cave, 1530-5 Honjo Oaza Onagara, Saiki, 〒876-0215 Oita, Tel: +81-972-56-5808.
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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|designated as a National Natural Monument.
|LED ligght installed.
|cave temporarily closed due to rockfall.
|cave reopened after removing the fragile rocks.
|a rock with a diameter of more than 1 m broke through the roof of the information center, cave and road in front closed.
小半鍾乳洞 (Onagarashōnyūdō, Small Half Limestone Cave) is located in the small village Honjo Oaza Onagara, on the banks of the Banjo River. It was hard to find any information on this cave the last time we researched. The results were two facts, the cave is the source of the Bansho river, and the cave has a colourful illumination which is a bit strange for foreign visitors. Actually many caves in Japan have coloured light, so that's not that exceptional. However, the current research revealed that both facts are untrue. The light was modernized in 2015 and incandescent lamps replaced by LED lamps, which are fortunately mostly white. And while there is a cave river it is actually a minor tributary of the Banjo River, not its source.
Much more important is the fact that the cave is located at the foot of a limestone cliff along Banjo river. Such cliffs tend to produce rockfall now and then, but it seems there were no problems until 2016 though. When small rocks fell down the cliff in January 2016, the cave was closed for two months and loose rocks removed from the cliff. But later that year, a rock with a diameter of more than 1 m broke through the roof of the information center. As a result, the cave and the road in front were both closed. According to their facebook page the cave has not yet been reopened. It seems the fact that it is a Natural Monument does not allow to do the necessary work to make it safe again.