Seven Wonders of the Middle Ages

Colosseum - Rome

The Colosseum is a giant amphitheatre in the centre of the city of Rome. Originally capable of seating 45,000–50,000 spectators, it was used for gladiatorial contests and public spectacles. It was built on a site just east of the Roman Forum, with construction starting between 70 and 72 AD under the emperor Vespasian. The amphitheatre, the largest ever built in the Roman Empire, was completed in 80 AD under Titus, with further modifications being made during Domitian's reign.
The Colosseum remained in use for nearly 500 years with the last recorded games being held there as late as the 6th century well after the traditional date of the fall of Rome in 476. As well as the traditional gladiatorial games, many other public spectacles were held there, such as mock sea battles, animal hunts, executions, re-enactments of famous battles, and dramas based on Classical mythology. The building eventually ceased to be used for entertainment in the early medieval era. It was later reused for such varied purposes as housing, workshops, quarters for a religious order, a fortress, a quarry and a Christian shrine.
Although it is now in a severely ruined condition due to damage caused by earthquakes and stone-robbers, the Colosseum has long been seen as an iconic symbol of Imperial Rome and is one of the finest surviving examples of Roman architecture. It is one of modern Rome's most popular tourist attractions and still has close connections with the Roman Catholic Church and the Pope leads a torchlit "Way of the Cross" procession to the amphitheatre each Good Friday

Physical description
The Colosseum measures 48 metres (157 ft / 165 Roman feet) high, 189 metres (615 ft / 640 Roman feet) long, and 156 metres (510 ft / 528 Roman feet) wide, with a base area of 6 acres. Unlike earlier amphitheatres, it was an entirely free-standing structure, constructed on flat ground rather than being built into an existing hillside or natural depression. Its outer wall originally measured 545 metres (1,788 ft / 1,835 Roman feet) and is estimated to have required over 100,000 cubic meters (3,531,466 ft³) of travertine stone held together by 300 tons of iron clamps. However, it has suffered extensive damage over the centuries, with large segments having collapsed following earthquakes. The north side of the perimeter wall is still standing; the distinctive triangular brick wedges at each end are modern additions, having been constructed in the early 19th century to shore up the wall. The remainder of the present-day exterior of the Colosseum is in fact the original interior wall.
The surviving part of the outer wall's monumental façade comprises three stories of superimposed arcades surmounted by a podium on which stands a tall attic, both of which are pierced by windows interspersed at regular intervals. The arcades are framed by half-columns of the Doric, Ionic, and Corinthian orders, while the attic is decorated with Corinthian pilasters. Each of the arches in the second- and third-floor arcades framed statues, probably honoring divinities and other figures from Classical mythology.
Two hundred and forty mast corbels were positioned around the top of the attic. They originally supported a retractable awning, known as the velarium, that kept the sun and rain off spectators. This consisted of a canvas-covered, net-like structure made of ropes, with a hole in the center. It covered two-thirds of the arena, and sloped down towards the center to catch the wind and provide a breeze for the audience. Sailors, specially enlisted from the Roman naval headquarters at Misenum and housed in the nearby Castra Misenatium, were used to work the velarium.
The Colosseum's huge crowd capacity made it essential that the venue could be filled or evacuated quickly. Its architects adopted solutions very similar to those used in modern stadiums to deal with the same problem. The amphitheatre was ringed by eighty entrances at ground level, 76 of which were used by ordinary spectators. Each entrance and exit was numbered, as was each staircase. The northern main entrance was reserved for the Roman Emperor and his aides, whilst the other three axial entrances were most likely used by the elite. All four axial entrances were richly decorated with painted stucco reliefs, of which fragments survive. Many of the original outer entrances have disappeared with the collapse of the perimeter wall, but entrances XXIII to LIV still survive.
Spectators were given tickets in the form of numbered pottery shards, which directed them to the appropriate section and row. They accessed their seats via vomitoria (singular vomitorium), passageways that opened into a tier of seats from below or behind. These quickly dispersed people into their seats and, upon conclusion of the event or in an emergency evacuation, could permit their exit within only a few minutes. The name vomitoria derived from the Latin word for a rapid discharge, from which English derives the word vomit.