Construction of the Submarine Mining Establishment at Valetta, Malta commenced in 1874 and was completed by 1877. The establishment was built in the Valetta Main Ditch, allowing it to connect with both the Grand Harbour and Marsamxett Harbour. This allowed for a single torpedo (mine) store and associated buildings to be built in the main ditch. The main buildings were built immediately opposite St John’s Curtain, with the loading room and two gun cotton stores (9 & 6 tons respectively) being built into the counterscarp wall opposite St John’s Bastion.
Cranes were located at each end of the ditch, one below Lascaris Counterguard for the Grand Harbour and the other below St Michael’s Bastion and Counterguard. The platform below St Michael’s can still be clearly seen although a home has been built on the top of it. The whole complex was linked by a narrow-gauge railway for the mines to be moved around on. Tunnels were cut through Lascaris Bastion to allow access to the crane there.
Apart from the tunnels and counterscarp gun cotton stores which were heavily modified during World War 2, little remains. Detailed plans, notes and photographs can be found at the UK National Archives WO 78/2942.
In 1900 the old Torpedo Store was converted to be the main Royal Engineer Workshop , see TNA WO 78/5326.
For more background on Submarine Ware between 1863 and 1907 see here.