Blackness Castle, located near the village of Blackness in Scotland, is a 15th-century fortress with a cool history. Built by Sir George Crichton in the 1440s, it served as a state prison and saw some famous prisoners like Cardinal Beaton. The castle got a major upgrade in the 16th century under Sir James Hamilton, making it a top-notch artillery fortification. It even survived a siege by Oliver Cromwell's army in 1650. Over the years, it had various uses from being a prison to an ammunition depot during World War I. Today, it's a restored historic site managed by Historic Environment Scotland. With its unique ship-like shape and stunning location on the Firth of Forth, Blackness Castle is definitely worth a visit!