Bellver Castle, located in Palma de Mallorca, Spain, is a unique Gothic-style castle built in the 14th century for King James II of Majorca. It stands out as one of the few circular castles in Europe, with a circular floor plan and round towers attached. Originally a royal residence, it later served as a military prison before becoming a popular tourist attraction and the city's History Museum. The castle's circular shape, surrounding wall, and inner yard make it a distinctive landmark on the island.