Alcove is the geographical and geological term for a steep-sided hollow in the side of an exposed rock face or cliff of a homogeneous rock type, that was water eroded.
Alcoves are weathering features common in dissected horizontal strata. Alcoves form where chemical and physical weathering is concentrated along horizontal discontinuities where water and salts concentrate, such as the contact between a sandstone and an underlying shale bed. In the case of layered sandstones, an alcove may later be enlarged by exfoliation of upper layers. This is commonly seen in the sandstone alcoves of the Colorado Plateau, like those in Navajo Sandstone.