3- Campo Marzio
In the imperial era many public buildings were built in the area lying between the Tiber and Quirinal in the north of Capitol. The emperor Augustus did build a vast amphiteatre dedicated to his nephew and son- in- low Marcellus just to the west foot of the Capitol. The arches of the theatre are well preserved.
By the 13th century the theatre had been converted into a fortress and in the 16th century on the ruins was built a great palace including a garden facing the Tiber.
To the north is still well-preserved the Portico of Octavia, built by Augustus in honor of his sister, is the only surviving portico of what used to be the monumental piazza of Circus Flaminius.
In Largo di Torre Argentina there is a site called Area Sacra in which are the remains of four temples dating from the era of the Republic. Some remains have been identified as the Curia of Pompey, a rectangular building housing a statue of Pompey, where the Senate met and where Julius Caesar was assassinated on 15 March 44 B.C.
Of the Domitian's Stadium is visible only the shape, because on the ruins of platforms have been built the mansions surrounding Piazza Navona. In Via del Corso, the old via Lata, we can admire the Column of Marcus Aurelius, clearly an imitation of the Column of Trajan, erected after the death of the Emperor in 180 A.D. to commemorate his victories over the barbarian tribes of the Danube.
Pantheon, roman Temple of all the gods, designed and built by Emperor Hadrian (A.D. 118-125) to replace an earlier temple built by Marcus Agrippa, son-in-low of Augustus. In the Middle Ages became a church.
The remains of the Temple of the Emperor Hadrian (eleven marble columns 49 ft (15 m) high) are visible on the southern side of Piazza di Pietra, they are now incorporated in a 17th century building that today houses the Roman Stock exchange (La Borsa).
There are two very important monuments dating from the reign of Emperor Augustus, the Altar of Peace (Ara Pacis), commissioned by the Senate in 13 B.C. to celebrate the peace created throughout the Mediterranean area by the Emperor Augustus, and the Mausoleum of Augustus, built in 28 B.C. by the Emperor as a tomb for himself and his descendants.
On the opposite bank of the Tiber stands the massive fortress of Castel Sant'Angelo. It takes its name from the statue of the Archangel Michael on its summit. It began life in A.D. 139 as the Emperor Hadrian's mausoleum and since then it has had many roles. In A.D. 270 the Tomb was incorporated into Aurelian Wall and fortified as outpost. In the Middle Ages it was citadel and prison, it was used as residence of the Popes in times of political unrest.