Vandals have damaged part of a Roman reconstruction in St Albans Verulamium Park.
Walkers found a hole in the metal grate boxing in a wall around the Roman Hypocaust, allowing access to the flints inside.
Although the Hypocaust is an 1,800-year-old central heating system preserved in the remains of a large Roman town house, the wall is a reproduction that has no historical value.
It is unclear whether the vandals were aware of this.
St Albans does have an ancient wall dated between AD 265 and 270 running along King Harry Lane, which is made with real Roman flint.
Chairman of St Albans Civic Society Tim Boatswain said they have been trying to discourage people from abusing the actual historical monument for about three years.
He said people cycle over it, clamber on it, and steal the stones.
Speaking about the vandalism of the replica wall, he said: “Flint is used quite a lot around St Albans but it’s not that easy to locate. The fact that they have bothered to cut a hole in the mesh suggests it is deliberate but it raises the whole issue again of the Roman wall.
“We know during the medieval era a lot of [the Roman wall] was moved and scrubbed down but I think we really need to alert people to the fact that this is a very important piece of heritage and we want to try and keep it for our children and our children’s children.
“If we don’t look after it and protect it, it will gradually disappear. It makes you despair but it’s a minority on the population and most people have a good respect and admiration for our heritage.
“It’s upsetting because they are taking something that is irreplaceable.”
SADC manage the damaged imitation wall.
Deputy head of commercial and development for SADC Tony Marmo said: “We have been made aware of the slight damage to the wall in front of the Hypocaust and will secure it. It’s not at all clear what has caused the problem.
“The missing stones were ordered from a supplier when the Hypocaust was built and were intended to look like the stones the Romans used to construct Verulamium. They are of no historical value.”
Anyone with information about heritage crimes should contact Herts police on 101.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here