More commonly known as the Redcliffe caves, but are more accurately Sand mines where the red sandstone rock was excavated and converted to sand for use by local industry. The two main uses of the sand where for the Glass trade who manufactured cheap dark green bottles and by the pottery trade who made slip to glaze their pottery with.
The history of the Redcliffe caves is unclear; there are only a few small references to them in the majority of books that have been consulted. The main references are:
- St Johns Hospital (1186) located on the now Redcliffe roundabout
- Dutchmen held as prisoners in the crypt of St Mary Redcliffe Church (1665)
- Spanish prisoners held in the caves (1741)
- French prisoners held in the caves (1744)
- The caves belonging to the glassworks and were used for storage (1784)
- An workers digging a broad gauge rail tunnel who broke into the tunnels (1868)
Of course, with every set of tunnels located near water, rumours quickly spread that they have been used for smuggling at some point in their history. Although there has been no reference has ever been found to them actually being used for smuggling activities, just several suggestions in various documents. The caves have also never been attributed with the slave trade in Bristol, although merchants from Bristol traded in slaves, they were never directly traded in Bristol itself.
Before World War 2 in 1938, the council did investigate using the caves as a Deep Shelter for the local population to use, but it was decided against. A small cave just down from the Phoenix Wharf entrance was used as an Air Raid shelter for thirty people.