The castle in Rimini was constructed in 1437 by Sigismondo Pandolfo Malatesta. What is visible today for visitors to see is only a fraction of the original building. The huge fortification once covered a large area but the great square towers and thick walls that are left standing are still impressive. What the initial plans entailed was a fort-like structure with a huge keep and drawbridges over a deep dyke. Castel Sismondo has served as a prison when it was under papacy rule and again during WWII.