Gladiatorial games, the bloodiest of ancient Rome's traditions, were probably held in the heart of genteel Cheshire, archaeologists say.
Two similar blocks were found in the arena in the 1960s
Experts have unearthed evidence in the remains of Chester Amphitheatre which suggests gladiators appeared there.
It was previously thought the arena was only used for ceremonial activities.
But archaeologists have found a stone block with iron fastening, suggesting that victims - human or animal - were chained up for gladiatorial spectacles.
Two similar blocks were found in the northern half of the arena, which is one of Britain's largest Roman amphitheatres, in the 1960s.
Experts believe the latest found in the centre is significant because it forms a row of anchor points along the axis of the arena for chaining victims.
Dan Garner, an archaeologist with Chester City Council, said: "Up to now, we have found human and animal remains to suggest that gladiatorial games may have taken place, but the discovery of the third chain block puts that suggestion almost beyond doubt.
"I dare say that people met a rather brutal end in Chester's arena some 1,900 years ago."
Tony Wilmott, an archaeologist at English Heritage, said the discovery of the block did not necessarily mean human slaves were chained.
He said: "It is possible that the blocks were also used for displaying exotic animals or for executing criminals who would be cast into the arena together with violent beasts.
Experts previously thought the arena was used for ceremonies
"What is certain is the Romans' flair for mass entertainment."
By chaining victims to these blocks along the long axis, the Romans were trying to ensure that spectators had the maximum view, Mr Wilmott added.
Excavations at the site have also uncovered evidence of eight vaulted stairways serving as entrances to the auditorium, evenly spaced around the arena.
Two foundation stones which could have formed the base of substantial columns have also been found, English Heritage said.
The findings were being presented at an international symposium on amphitheatres in Chester on 17 and 18 February.
Mr Wilmott said the findings would change historians' understanding of Roman Chester.