Ponte Sant'Angelo, Castel Sant'Angelo, Mausoleum of Hadrian, Parco Adriano, Rome, Italy - The Castle was built in 123 AD by Emperor Hadrian as a monumental tomb for himself and his family. There is a secret corridor (Passetto di Borgo) that connects it to the Leonine walls and the Vatican, a passageway for the pope in dangerous situations. There were many popes who used it. Pope Alexander VI used it to escape to the castle from Charles VIII troops. And Clement VII who used it to escape the Landsknechts during the Sack of Rome in 1527, dodging a hailstorm of gunshots as he crossed.
Pantheon, Rome, Italy - The former Temple is one of the best-preserved of all Ancient Roman buildings, it is now a church. The present building was completed by emperor Hadrian, it is thought he also was the architect, dedicated approximately 126 AD. Nearly two thousand years after it was built, the Pantheon's roof is still the world's largest unreinforced concrete dome. The concrete used was gradually thinned towards the summit. They would mix clay jars into the concrete to create pockets of air to lighten the weight of the roof. The height of the oculus and the diameter of the interior circle are both the same, 142 feet.
Beautiful Sunset, St Peter's Basilica, Vatican City, Rome, Italy - St. Peter's is the most renowned work of Renaissance architecture, it is also the largest church in the world. Catholic tradition holds that the Basilica is the burial site of Saint Peter, one of Jesus's Apostles and also considered the first Pope. Peter, like Jesus, was crucified (Caravaggio painted the incredible Crucifixion of St. Peter). The bridge in the foreground over the Tiber is Ponte Sant'Angelo, completed in 134 AD by Roman Emperor Hadrian.