The world's smallest castle is a 1.5 meter tall stone tower in Scotland - Apparently.
The Crow Castle, located in Argyll and Bute, Scotland, is a miniature castle that was built in the 15th century as a fortified tower house. It is only 1.5 meters (4.9 feet) tall and has a floor area of just 3.6 square meters (38.8 square feet). The castle is considered a rare example of a "pele tower," a type of small, fortified dwelling that was common in medieval Scotland.