The caves were dug to provide sand for glass making and pottery production. They were dug into the Triassic red sandstone cliffs, which give the area its name, adjacent to the southern side of Bristol Harbour, behind Phoenix Wharf and Redcliffe Wharf. The first excavation was during the Middle Ages but the majority of the digging was during the mid 17th and early 19th centuries. In the larger caverns the stone columns supporting the roof were not sufficient and these have been supplemented with wall arches made of stone, brick and more recently of concrete.
