rock basin
/ˌrɒk ˈbeɪsn/noun
A basin-shaped hollow in rock, especially one of natural origin; (Geomorphology ) a large depression in a rocky area that was formed by glacial erosion and is commonly filled by a lake.
Origin
Mid 18th century; earliest use found in William Borlase (1696–1772), antiquary and naturalist. From rock + basin.