Castel Sant’Angelo has to be one of the best museums in Rome as parts of this renowned museum in Rome are as old as 1,900 years. The castle was originally built as the mausoleum for the Roman Emperor Hadrian. But in the middle ages, it was significantly renovated. Currently, it houses a museum namely the Museo Nazionale di Castel Sant’Angelo. Besides appreciating the magnificent structure of the castle, you can find some rare collection of medieval weaponry and Renaissance paintings.