Built as a mausoleum for the Emperor Publius Aelius Trajan Hadrian and a dynastic sepulchre for the Antonine family, and later becoming a sort of fortress for the defence of the city, the imposing Castel Sant'Angelo now houses an interesting museum. The museum itinerary winds its way through rooms dating back to Roman times and rooms elegantly decorated with stucco and frescoes during the 16th century. With special thematic tours, it is also possible to discover rooms that are not usually open to the public: these are the infamous historical prisons created at the time of Alexander VI, the Passetto di Borgo and the highly refined Stufetta di Clemente VII, the heated bath that the Medici pontiff had built inside the fort. Last but not least, we cannot fail to mention the sweeping views of the city from the Giretto and even more so from the Terrazzo dell'Angelo.