Gibside, a Grade I listed park and gardens in Gateshead run by the National Trust, has been hit by 30 crimes over the past 12 months, the charity has said.
Two separate night-time break-ins took place at the site on 30 July and 1 August, causing damage to parts of the property and forcing the café to temporarily close.
Pattern of vandalism and anti-social behaviour
Eric Wilton, general manager of Gibside, said vandalism over the previous year had included damage to play equipment. Overnight campers have also set fire to the gardens and burned deckchairs.
Wilton reported an increase in after-hours anti-social behaviour at the site overall.
"Repeatedly arriving at work to find scenes of vandalism and destruction, then having to spend time cleaning up the aftermath and dealing with the police, is extremely demoralising," he said.
"As a charity, the cost of replacing items and repairing damage, not to mention income lost through needing to temporarily close our cafes, has hit us hard."
Security response and investigation
In response, the National Trust has increased security patrols at Gibside and installed more CCTV.
Northumbria Police said it was investigating the break-ins and asked for witnesses to come forward.
