Police are stepping up efforts to tackle vandalism and anti-social behaviour at Dinorwig Quarry.
Rural crime officers say the site has been repeatedly hit by repeated incidents of criminal damage and arson, including damage to historic slate structures and broken windows.
North Wales Police says it will work closely with landowners to protect the area, using additional security measures including CCTV cameras and regular hi-vis and covert patrols aimed at deterring and tracking down offenders.
A NWP spokesperson said the quarry was "not only an important part of the area's industrial and cultural history" but also forms part of the UNESCO world heritage site - namely the slate landscape of North West Wales.
They added: "The site contains listed buildings and scheduled monuments, making it a protected heritage asset of national and international significance."
"Damage to historic structures and monuments has a lasting impact and can result in the permanent loss of important heritage features."
"Due to the nature of the site, it is afforded additional protection in law, and those found responsible for committing offences there can expect to be dealt with robustly."
Anyone with information about damage to heritage sites or any suspicious activity should contact North Wales Police on 101 or via the live web chat.
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