The Colosseum

The walk goes from the outside in, and then down: the wall, the doors, the seats, the arena, the floor under it. The last stops are what stands around the building, and what was happening in China.

1. The outer wall: four storeys and thousands of holes

The wall is about 48 metres high. The building is an oval, 189 metres long and 156 wide. The stone is travertine from quarries near Tivoli, about 100,000 cubic metres of it.

Read it from the bottom. Three rings of arches, eighty arches to a ring, and a solid top storey. The half-columns between the arches change at each level: plain Tuscan at the bottom, Ionic with scrolls above, leafy Corinthian above that. Architects from the Renaissance on copied this stack on palaces all over Europe.

The wall is pitted with holes. They are not from weapons. The blocks were held together by iron clamps set in lead, about 300 tonnes of iron in all. In the Middle Ages people dug the metal out, block by block.

At each end of the standing wall is a great sloping wedge of brick. They are props, built in 1807 and 1826, when the broken ends were about to fall.

2. The doors: a number over every arch

Of the eighty arches on the ground, seventy-six were public doors and had a Roman numeral above them. On the north side you can still read them. A spectator carried a token of clay or bone marked with a door, a section and a row.

The four doors on the main axes had no number. Two were for the emperor and for officials. Two were for the performers. Through one of them, at the east end, the dead were carried out.

Inside, stairs and passages fan out so that streams of people never cross. The exits were called vomitoria, from the Latin for "to spew out". Every big stadium built since works the same way.

3. The seats: Rome ranked in stone

Where you sat was fixed by law. The front platform, nearest the sand, was for senators, who brought their own chairs; some of their names are cut into the stone. Above them sat the knights, then ordinary citizens, then the poor. At the very top, on wooden benches under a roofed gallery, sat women and slaves.

The emperor had a box on the short axis. Opposite him sat the Vestal Virgins, the only women allowed near the front.

How many it held is not settled. A list of the 300s says 87,000. Most modern estimates, from the length of the seating, come to about 50,000.

The white marble seats you see in one section were put back in the 1930s as a sample, and not very accurately.

4. The arena: a day at the games

Arena is the Latin word for sand. The floor was wood covered with sand, about 83 metres by 48. The sand soaked up blood.

A full day had three parts. In the morning, hunts: lions, leopards, bears, elephants, ostriches, brought from the edges of the empire and killed by trained hunters. At midday, executions of criminals. In the afternoon, the gladiators.

Gladiators fought in set pairs with different kit: a net-man with a trident against a man with a sword and a smooth helmet, and so on. There was a referee. A beaten man could appeal, and the giver of the games decided.

For the opening in AD 80 the historian Cassius Dio, writing more than a century later, says nine thousand animals were killed. The numbers in ancient writers are large and cannot be checked.

The last gladiator fights known in Rome were in the 430s. The beast hunts went on until 523.

5. Under the floor: the machine room

The walls you see in the pit are the hypogeum, "the place under the ground". It was added by the emperor Domitian, Titus's brother, a few years after the opening. There are two storeys of corridors and cells.

Animals were kept in cages here. Men turned capstans, and wooden lifts rose in shafts to trapdoors in the floor. The German archaeologist Heinz-Jürgen Beste, who studied the marks in the walls, found the places of 28 lifts for large animals round the edge, and of many more hoists added later. A leopard could appear in the middle of the arena as if from nowhere.

A working copy of one lift was built in 2015 and stands in the hypogeum.

A tunnel ran from here to the gladiators' school next door, so the fighters reached the arena without passing through the crowd.

Before this basement was built, the arena may have been flooded for a show. Dio says Titus filled it with water for a sea fight at the opening. Some scholars accept it. Others think the sea fight was held in a basin across the river. Once the basement existed, flooding was impossible.

6. The sky: an awning worked by sailors

Round the top storey, outside, is a row of stone brackets, 240 of them. Each held a wooden mast. From the masts ropes ran in towards the centre and carried strips of cloth, the velarium, which shaded the seats.

It was handled by sailors from the imperial fleet at Misenum, on the Bay of Naples, who were quartered nearby for the purpose. They knew ropes and canvas.

7. Who paid: a lake and a temple

The ground was Nero's lake. The money was Jerusalem's. In 1995 the scholar Géza Alföldy studied a stone inside the building that carries a later inscription. Under it are the peg holes of older bronze letters. From the holes he read: the emperor Vespasian ordered the new amphitheatre to be built from the spoils of war.

Walk ten minutes to the Arch of Titus, at the top of the Forum. On the inside of the arch Roman soldiers carry the seven-branched lampstand out of the Temple. That is the war that paid for the building behind you.

It is often said that tens of thousands of Jewish captives built it. That is possible, and no ancient source says so.

The name came later. Near the building stood a bronze statue of Nero more than thirty metres high, the Colossus. The amphitheatre took its nickname from the statue, and the name is first found around the year 1000. The statue is gone. Its base was beside the road, between the amphitheatre and the temple on the rise.

8. After the games: fortress, quarry, garden, church

When the games ended the building found other uses. People lived and kept workshops in the arches. In the 1100s a Roman clan, the Frangipani, made it their castle.

The south side stood on softer ground. The earthquake of 1349 threw it down. The heap of cut stone was too good to leave. It went into St Peter's, the Palazzo Venezia, the Palazzo Barberini and the steps of the river port.

In 1749 Pope Benedict XIV stopped the quarrying. He declared the place holy to the Christians believed to have died here, and set the Stations of the Cross round the arena. The photograph of the 1860s shows them, with a cross in the middle.

By then it was also a garden. In 1855 the English doctor Richard Deakin published a book on the plants growing on the ruin and listed 420 kinds. After 1870 the archaeologists pulled them out.

The arena was dug out in 1874 and the Stations were removed. A cross was put back in 1926, at the side. Every Good Friday the Pope leads the Way of the Cross here, by torchlight.

Since 1999 the building has had one more job. When a death sentence somewhere in the world is commuted, or a country gives up the death penalty, its night lighting changes from white to gold.

9. Around the building

The Arch of Constantine, beside the amphitheatre, was put up in AD 315 for the emperor's victory over a rival. Much of its sculpture was taken from monuments two hundred years older, and the heads recut. You can walk round it for nothing.

On the east side, below street level, is half of a small oval of seats. This is the Ludus Magnus, the biggest gladiator school in Rome, with its own practice arena. Look down into it from the pavement.

Your ticket also covers the Roman Forum and the Palatine Hill, across the road. They need half a day of their own.

10. The same years in China

When the building opened in AD 80, China was the Eastern Han (AD 25–220), under Emperor Zhang. Each empire had heard of the other. The Chinese called Rome Da Qin (221–206 BC), "Great Qin".

In AD 97, seventeen years after the opening, the Han general Ban Chao sent an envoy named Gan Ying west to reach Da Qin. He got as far as a great sea, probably the Persian Gulf. Sailors there told him the crossing could take two years, and he turned back. He is the nearest any Han official came to seeing this building.

Around AD 105, in the Han capital Luoyang, the court official Cai Lun reported an improved way of making paper. Rome at that date wrote on papyrus and wax.

Han China had its own arena shows, called the "hundred entertainments": wrestling, acrobats, sword-swallowers, and men matched against tigers and bulls. Tomb carvings show them. They were court and festival shows. Nothing in China was built on this scale to hold them.

11. On the page and on the screen

An old saying, which medieval pilgrims carried home, ties the fate of the world to this building. Byron put it into English in 1818.

While stands the Coliseum, Rome shall stand; When falls the Coliseum, Rome shall fall; And when Rome falls—the World.

Byron, Childe Harold's Pilgrimage, Canto IV (1818)

Pollice Verso (Jean-Léon Gérôme, 1872). A gladiator stands over his beaten opponent and looks up at a row of women who jab their thumbs down. The painting invented the gesture for the modern world. Ridley Scott has said that seeing it persuaded him to make Gladiator.

Roman Holiday (1953). The princess, the reporter and the photographer visit the inside of the building on their day out; the scene was shot here.

The Way of the Dragon (1972). Bruce Lee wrote, directed and starred. His fight with Chuck Norris is set among these arches. The crew filmed here briefly; most of the fight was shot on a set built in Hong Kong.

Gladiator (2000). None of it was filmed here. Part of the arena was built in Malta and the rest was made by computer.

In May 2003 Paul McCartney played inside the building to an audience of about four hundred, the first rock concert in the arena.