Fort Casey State Park preserves one of the old coastal forts built to defend Puget Sound. The concrete batteries, disappearing guns, grassy parade grounds, and Admiralty Head Lighthouse make it more atmospheric than a simple military stop.
It sits by the Coupeville ferry terminal, so it is easy to pair with the Port Townsend boat. Walk the gun batteries, then look west across Admiralty Inlet toward the Olympics and north toward the shipping lanes.