A building within Dinorwig Quarry, near Caernarfon, was set ablaze at around 1pm on Saturday, October 26.
The fire was reported by a member of the public, with fire and rescue service teams able to stop the spread before more damage could be done.
North Wales Police have criticised those responsible for the crime, with the arson showing a “blatant lack of respect” for a site with “hundreds of years of history and meaning”.
A North Wales Police spokesperson said: “A deliberate fire was discovered by a member of the public at Dinorwig Quarry, specifically in the first drum house on the incline directly opposite the Lake Railway Shop & Cafe.
“North Wales Fire & Rescue Service were called and luckily the fire was extinguished in time before it could spread and completely damage the drum house roof.
“Dinorwig Quarry is a UNESCO World Heritage Site and the drum house is classed as a scheduled monument.
“Scheduled monuments are nationally important monuments that have been afforded statutory protection through their inclusion in the Schedule of monuments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979.
“This abhorrent act of damage is mindless and extremely disappointing and shows a blatant lack of respect towards a historic site with hundreds of years of history and meaning.
“If anyone has any information in relation to this, please contact 101 quoting reference number 24000916057.”
