Stack Rock Fort
Herbrandston, United Kingdom
Stack Rock Fort is a fort built on a small island in the Milford Haven Waterway, Pembrokeshire, Wales. A 3-gun fort was built between 1850 and 1852, and then upgraded from 1859 to 1871 with a new building that completely encased the original gun tower. It is now a Grade II* listed building and a scheduled monument (registered SAM number PE334).
Fort data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).