The Fortifications of Monaco are a series of defensive structures built to protect the principality from invasions. The most notable is the Prince's Palace, which dates back to the 13th century and has been expanded over the years. The walls and towers surrounding the palace were designed to deter attackers and provide a strategic vantage point. In addition to the palace, the Fort Antoine is another significant fortification, constructed in the 18th century. This military fortress was built to defend the harbor and is now used as an open-air theater. Together, these fortifications reflect Monaco's rich history and strategic importance in the Mediterranean.