Police officers are hunting the unknown individuals who turned part of a Perthshire estate into their own personal playground.
Unnoticed by owners the group felled trees within Cowden Wood to create mountain bike jumps and even a basketball court.
They also erected a “gang hut” on the secluded site, between Comrie and the Cultybraggan Prisoner of War Camp, and created a shooting range.
Portals had been cut in the sides of the hut, with targets found some 50 metres away.
There was also evidence that in addition to mountain bikes, access had been taken with a small quad bike.
The woods, part of Cultybraggan Farm, have been nurtured by landowner Dr James Irvine and his team to form a wildlife-friendly area for the benefit of the entire community.
He has always welcomed “responsible access” but has sadly seen his trust breached on more than one occasion by vandals.
Never before, however, has the damage been so significant and so brazen, with an astonishing recreation site created away from prying eyes.
Police cordoned-off the entire area as they began investigations into the vandalism which has left locals bemused.
Dr Irvine said: “Sadly we do get quite a few vandals but I have never seen anything like this.
“There is a hut, a basketball court and a mountain bike track with jumps.
“They have created all this in Cowden Wood, which is one small part of our farm, about half a mile from the farmhouse.
“It is essentially an environment wood where we have planted trees to encourage wildlife and do not use it for any commercial purposes.
“It contributes greatly to the local environment and to the local wildlife and we are always happy for people to walk here as long as access is taken responsibly.
“Of course we are also deeply unhappy when people abuse that — particularly when they do so as spectacularly as they have here.
“There has been significant damage and of course that results in a loss of amenity for everyone.”
Dr Irvine said he was also deeply concerned by evidence that the people who built the hut had been starting fires, with evidence of fires in the woods nearby. Fire-lighters were found on a shelf.
Police Scotland has issued an appeal to the public seeking information about the damage, which is understood to have taken place between April 1 and June 12.
A spokesperson said: “The woods are private property and the landowner has not given permission for any construction or any recreational activities other than walking to take place in the woods.
“A number of saplings have been felled in the construction of this hut and area, also without permission of the landowner.”
Anyone with information about the offence is asked to call Police Scotland on 101 or contact Crimestoppers anonymously on 0800 555 111.