Castel Sant’Angelo, originally constructed as a mausoleum for Emperor Hadrian in the 2nd century, has served multiple purposes throughout history, including as a fortress for the Pope during the Middle Ages and as a prison where notable figures like Giordano Bruno were held. Its impressive interior and courtyard are filled with a rich blend of architectural elements and artifacts from imperial and medieval Rome, as well as Renaissance masterpieces, making it a significant historical and cultural landmark.