The Ongryonsan Stone River is in Pujon County, South Hamgyong Province of Korea. It is called so because water flows under the river-shaped stony field along the southwestern slope of Mt. Ongryon.

There were lots of rocks on the summit of Mt. Ongryon which is 2,164 metres above the sea level and some of them dropped along the river valley to be scattered there, making the Ongryonsan Stone River. The stone river was formed between about 120,000 years ago and about 6,000 years ago.

The Ongryonsan Stone River is the biggest and rarest of the stone rivers in Korea.

The stony field is 120 metres wide and 700 metres long while the inclination of its surface is about 10 degrees.

Stones have been piled up, which is 4 to 5 metres thick on an average and most of them are about 1 to 4 metres across.

The water flows under the stony field, making a big sound even in the dry season.

The water flows like an underground water to the end of the stone river where it comes up to the ground.

At present, the Ongryonsan Stone River is about 2 kilometres long when the part covered by plants is added.

The Ongryonsan Stone River showing the mysteriousness of the nature has been designated as a natural monument for its scientific and picturesque significance.