Horse Sand Fort
Here is yet another British submarine base that was used by the Royal Commission at one point. Horse Sand Fort is located at the strait of Solent in Portsmouth. Originally meant to be a part of the Palmerston Forts, the British used it during WW2 and equipped it with advanced weapons and defenses. The iron-armor walls and gates were reinforced with granite and concrete. AmaZing Venues later bought it.

Horse Sand Fort
Puget Sound Naval Shipyard
Puget Sound Naval Shipyard and Intermediate Maintenance Facility is located in Washington, U.S. It has been operating since 1891 as part of a navy recycling program. It now has a submarine tender, four decommissioned aircraft carriers, and 16 nuclear submarines for scrapping. It has a reserve fleet as well. Here is a fun fact for you: the PSNS is the only US shipyard facility that can recycle nuclear ships.

Puget Sound Naval Shipyard