For a long time it was a peculiarly English assumption that the amphitheatre at Chester would have been used mostly for military training - parade drill for the legionaries of Legio XX Valeria Victrix, who garrisoned Deva for most of the Roman occupation. The assumption was tidy and dignified and almost completely wrong. Everything the excavators have actually found points to the same thing that Roman amphitheatres are known for everywhere else: cockfighting, bull-baiting, combat sports including classical boxing and wrestling and, most importantly, gladiatorial combat. Real fights. Real blood. Real animals dying for entertainment. The audience was largely military - legionaries on leave, their families, the civilian camp followers and merchants of the canabae outside the fortress walls - but the violence they came to watch was the same violence that ran through the empire, from Carthage to Caerleon to the Colosseum. Eight to ten thousand people sat on this curved seating bank in the second and third centuries, and what they sat to watch was people and animals being killed for sport.

The first amphitheatre at Chester was probably a simple structure built by Legio II Adiutrix during their brief posting in the late seventies AD - light timber bones, modest seating, fit for a frontier. When Legio II Adiutrix was reassigned to the Danube in 86, the incoming Legio XX Valeria Victrix rebuilt it more substantially. It fell into disuse around 122 when Legio XX was pulled north to build Hadrian's Wall, and was probably half-derelict for decades until the legion returned around 275 and put it back into operation. The most ambitious rebuilding came around AD 200, when the amphitheatre was largely reconstructed and the seating capacity roughly doubled. A massive new outer wall was built, its foundations 2.7 metres wide and 1.3 metres deep - a serious piece of construction, the kind of investment a permanent garrison makes in its permanent entertainment. By the early fourth century the place was already past its peak. By around 350, it had been abandoned.

When the Romans left Britain, the amphitheatre's masonry was scavenged - cut stone is precious, and the great curved walls of Deva became the foundations of medieval Chester elsewhere. What remained was a saucer-shaped depression in the ground, useful for bear-baiting and public executions in the early modern period. Then, slowly, the depression filled with refuse and erosion and forgotten dirt. By the eighteenth century, the awkward contours of the buried amphitheatre - too steep for a road, too uneven for sensible building - had become a passive form of preservation. Two Georgian houses were built on it: Dee House on the south end of the arena, and St John's House on the north. The southern half of the amphitheatre still lies under Dee House and the modern County Court car park today. Excavation has therefore been one-sided. We know far more about the north half than the south. We may have lost things in the south we can no longer recover.

Between 2000 and 2006, Chester City Council - joined by English Heritage from 2004 - undertook the most thorough excavation the site had ever seen. Three areas of the seating bank and arena were investigated. Co-directors Dan Garner and Tony Wilmott published findings that resolved a long-running scholarly debate about whether the original timber amphitheatre had been a separate, earlier structure; in fact, the timber grillage was simply the base on which the later stone seating was set. Other claims - including a History Channel documentary's contention that the amphitheatre might have inspired the King Arthur Round Table legend - were quietly dismissed by English Heritage as having no archaeological basis. The dig also showed how complete the southern remains might still be: substantial sections of the curved outer wall, vomitoria entrances, and probably even arena-floor features remain undisturbed beneath modern paving.

What visitors see today is roughly half a Roman amphitheatre. The northern curved seating bank is laid out clearly in the grass below the city walls, with the arena floor exposed and walkable. In August 2010, a fifty-metre trompe l'oeil mural by the artist Gary Drostle was added to the walkway wall to complete what the eye cannot otherwise see - a continuation of the exposed northern half into a painted, full ellipse, complete with red marble arena wall, doorways and vomitoria, and the central tethering stone where animals would have been chained. Drostle worked with five painters across six weeks on two six-metre scaffolding towers, using Keim mineral paints invented in 1878 - a silicate paint that bonds chemically with the masonry rather than just sitting on top of it, so the image should last for decades without flaking. The result is the closest most people will ever come to standing inside a working Roman amphitheatre. From the city walls above, looking down, it is genuinely possible to see eight thousand seats.