Fort Zverev, Kronstadt
Official version - this place was used as warehouse of flammable materials and there was a fire, the bricks melted.

But combustion temperature of fuel oil (350°C) is not sufficient to melt bricks (1200°C).

A rock-cut tomb was discovered in the village of Ohanavan, in the Kasakh gorge, which, according to preliminary estimates by experts, dates back to the period of V-VII or XII-XIII centuries. It will be studied in detail in the near future.

Source: https://am.sputniknews.ru/amp/20240217/otkrytiya-budut-vpechatlyayuschimi-kakaya-usypalnitsa-byla-obnaruzhena-u-sela-oganavan-72407783.html

Moscow, Khokhlovskiy pereulok, 2/1

Looks like at least 1 floor is below ground level. The entrance is cut through in the place of the window