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Photo: Sixtus, CC BY-SA 3.0 via Wikimedia Commons
A great little cathedral to visit, lovingly looked after by Irish Dominicans. There is an excavated older church below the medieval church you enter and a Mithraeum (temple to Mithras, whose cult was very popular with Roman soldiers from the 1st to 4th century AD) below that. The only place in Rome to hear the underground river that flows beneath the city.
The Basilica of Saint Clement is a Latin Catholic minor basilica dedicated to Pope Clement I located in Rome, Italy. Archaeologically speaking, the structure is a three-tiered complex of buildings: (1) the present basilica built just before the year 1100 during the height of the Middle Ages; (2) beneath the present basilica is a 4th-century basilica that had been converted out of the home of a Roman nobleman, part of which had in the 1st century briefly served as an early church, and the basement of which had in the 2nd century briefly served as a mithraeum; (3) the home of the Roman nobleman had been built on the foundations of republican era villa and warehouse that had been destroyed in the Great Fire of AD 64.
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This is the attractive park on the hillside directly west of the Colosseum. Visible ruins in the area come from the Baths of Trajan. These baths were built on the top of the ruins of Domus Aurea - the Golden House of Nero (the Colosseum was built on the drained site of Nero's lake). The area underneath the park contains an enormous area from Nero's villa. It was restored at great expense in the 1980s and 1990s, opened to the public, and then closed again after a few years when it began to leak!
Known properly as the Flavian Amphitheatre, this most famous of Roman landmarks takes its name from the giant statue of the emperor Nero that once stood near this location. The amphitheatre was capable of seating 50,000 spectators for animal fights and gladiatorial combats. It was a project started by the Emperor Vespasian in 72 and completed by his son Domitian sometime in the 80s. The Colosseum when completed measured 48 m high, 188 m in length, and 156 m in width. The wooden arena floor was 86 m by 54 m, and covered by sand.;
Expect a long queue and an even longer wait. You can skip the queue if you decide to take a tour, but if you don't want a tour, you can STILL skip the queue. If you walk to the entrance for the Roman Forum, you can buy tickets there which allow you to bypass the queues. You can also buy tickets online. There are lots of people offering tours in English just outside the entrance to the Colosseum. Inside you can take a tour (English, Spanish, or German) every 30 minutes or so for an additional fee. The tours are given by knowledgeable archeologists, but they don't take you to any areas you couldn't visit on your own.
Unusual and fascinating round church dedicated to St. Stephen. It is the national church of Hungary in Rome. Dating from the 5th century this is believed to be the largest round church in the world. Charles Dickens described its wall paintings of martyrdom and butchery as "hideous". A good starting point to visit the attractions of the Celio Hill (see Rome/Aventino-Testaccio).
According to the legendary passio, two brothers, John and Paul, who were officials at the imperial court, suffered martyrdom in 362 in their home on the Caelian hill, during the reign of emperor Flavius Claudius Julianus. This basilica dedicated to these two Roman officers was erected starting from 398 and was used first as a domus ecclesiae by the Christian community.
Arco di Costantino
Located a short walk west of the Colosseum, this well-preserved monumental arch was erected (soon after 315) to commemorate the victory of Constantine, the first Christian emperor, over his rival Maxentius at the Battle of the Milvian Bridge in 312. In general design, the Arch of Constantine imitates the century-earlier Arch of Septimius Severus (nearby in the Forum). The three arches are decorated utilizing mainly materials plundered from other imperial monuments by Trajan, Hadrian and Marcus Aurelius. The quality of its sculptural decoration, however, betrays the slow degradation that Classical Roman sculpture had experienced in the 3rd century AD.
The chains that allegedly held St. Peter are displayed in a case before the altar. More importantly, contains the impressive statue of Moses by Michelangelo. It's close to the Colosseum, but a little hard to find. Take the steps opposite the Colosseum on Via dei Fori Imperiali, cross the road at the top and seek directions. Also reachable through steps to the right leading off Via Cavour.