One of the best things about Castel Sant'Angelo is that you can book tickets for it online. Besides this, if you happen to be a citizen of the European Union, you are eligible for a free entry. All students and academicians studying arts, or architecture are allowed a free entry.
Also known as Mausoleum of Hadrian, the main building is cylindrical in shape. The Roman Emperor Hadrian wanted to be immortal, and so, he chose to build the mausoleum to remind people of him.
Down the annals of time, as the reign of kings and popes changed hands, it came to be used as a fortress, a castle and is now serves as a museum. It was one of the most popular asylums of those running away from trouble. The Pope could reach the mausoleum and seek refuge and privacy through a secret route.
The Castel used to be the tallest building in Rome once upon a time, but with time and the advancement in building technology, the building lost its title to other modern structures. Its construction dates back to 135-139 AD.
The building is also known as Hadrianeum. Its architects wanted to give a circular architecture to a square enclosure. The mausoleum thus originally had a circular shape, or was a cylinder. King Hadrian's remains were placed in the mausoleum only a year had elapsed since his demise. His wife, Sarbina, also figures in the mausoleum as does their adopted son, Lucius Aelius. It became a trend to keep the ashes of all emperors here till 217 AD.