The commanding presence of Castel Sant' Angelo across the banks of the Tiber is impressive to say the least...until looking at the illustration on top of page 248 in the Eyewitness Guidebook. What we see today is considered Rome's stronghold that in the 14th century was claimed by The Vatican as a "safehouse" for Popes. The Eyewitness illustration details the striking, yet simple beauty of a mausoleum built by Hadrian in 139 A.D. to serve as final resting place for him and all the families of the Antonine and Severine emperors through Caracalla. As for the dead, typically their memories are about all that's left.
Converting a mausoleum into a castle fortress involved leveled layers of both horizontal and vertical expansions - all of which maintain the original circular form. For L10,000, it's worth the effort to enjoy the tour which starts with lower courtyards littered with artillery which you'll wander around until the path enters and follows the same round, slightly ascending course thru the inner layers. Aside from also serving as a prison and citadel, what you see today is more from residencial apartments - turned museum where the Vatican's population sought refuge.
The actual highlight of Sant' Angelo are the 360-degree views from balconies at all different levels. A snack bar/patio cafe are located on the upper level. A.M. visits net great views of The Vatican; P.M. back into the city based on the sun's position. The other main attraction not to be missed is the Ponte (bridge) which Hadrian built linking his mausoleum to the city across the Tiber. Original parts were incorporated into the current bridge after it collapsed in 1450; the crowning touch from Bernini and his 17th century students sculpting the angels which line the bridge and guide your way across.
The inspiration for Hadrian's mausoleum came from the 29 B.C. version built by Caesar Augustus which lies further up on opposite side of the river. To say the final resting place of Rome's first Emperor has fallen into a sad state of disarray would be a gross understatement. After supposedly being used over the years for a fortress, vineyard, and theatre auditorium among other things, it's completely abandoned and disgustingly littered today. If Augustus could issue a monumental decree today like the Biblical one that lured Mary and Joseph to Bethlehem, I've got to believe it would have something to do with honoring him and his legacies by fixing the place up! Maybe there's hope. The 13 B.C. Ara Pacis (Altar of Peace) across the street, built for the uniting efforts of Augustus, was completely sealed off for renovations...as was the Palatine Hill's House of Livia; the modest home with many surviving frescoes where Augustus lived with his wife.