Ancient fortress in the middle of the lake

Por-Bazhyn was built thirteen centuries ago. Its total area is about 3.3 hectares. It is almost impossible to reach the fortress. Only by air or by cross-country vehicle. Moreover, the second option is available only in the dry season. For the first time this building in the middle of the lake was discovered just over a century ago, very near the border of Russia with Mongolia. On the territory of archaeological excavations, no human remains were found, which confirms the hypothesis of a timely escape of local residents. Before the fortress was destroyed by fire. There is also a version that the fortress was not burned, but destroyed due to a powerful earthquake. In the near future this memo of architecture can disappear under water.