Fort Frederick
Nelson Mandela Bay Metropolitan Municipality, South Africa
Fort Frederick in Port Elizabeth, South Africa, was built in 1799 in order to stop the French from conquering the Cape Colony during the Napoleonic Wars and played a vital role in establishing British rule in South Africa in combination with the Battle of Blaauwberg. The fort has never fired a shot from its guns.
Fort data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).