Heritage Open Day: An inclusive celebration of music of all genres amidst the vibrant cultural heritage of Southampton. Culminating in an annual multi-venue music festival on 13/14th September. We exist for the musicians and the people of Southampton. Castle Vault is the biggest, and one of the oldest, vaults in Southampton, built to store the King’s wine at a time when the port was at the centre of the wine trade. Ships were able to offload the casks onto a quay directly outside the vault, as the water was very close to this section of the walls during the medieval period.