A mountain biker made a shocking discovery during a ride with friends.
Chris Williams, who was on a weekly ride, spotted a long plank of wood that had been covered with nails and covered over with soil.
Luckily, 51-year-old Chris and his friends managed to stop just before riding over the makeshift trap, which he believes had been set up to try to "catch people out".
He found the alleged trap on Monday, July 8, while out riding at around 8pm near Blaenavon .
The 1.3-metre plank of wood, which had 170 nails through it, was found on a popular mountain bike trail; the forest trail is from the Blorange mountain leading onto Blaenavon Road, in Abergavenny.
Chris believes it's a "deliberate trap for someone".
He said: "They've basically put put it in the ground, dug a little trench, put the timber in the ground so the nails are sticking up above the timber and put a dusting of soil over it.
"Lucky enough we were slowing down to take a corner. If we'd been going a lot faster we wouldn't have seen it.
"Where they put it was by a bank that leads onto a main road, so if had blown the tyres out, the chances are you could've fell off that bike, into the road in front of a lorry or a car."
He added: "It's a footpath and people have been using it for years for push bikes. My biggest concern is a kid walking over it - a kid or an animal. Why would you want to do something like that?"
It's the latest in a series of similar dangerous acts seemingly targeting mountain paths like this. In February, someone strung barbed wire at head height between two trees on a mountain path in the Rhondda.
What do to if you have a road accident:
The land where Chris found the nails belongs to Natural Resources Wales.
Peter Cloke, land management team leader for Natural Resources Wales, said: “People use our forests as a great way to enjoy our environment and get healthy in the outdoors, but people need to be safe while doing so.
“Sabotaging paths in woodlands is incredibly dangerous and puts people and animals at risk."
Mr Cloke added: “If anyone sees evidence of dangerous activity or items in the forest we manage, please report it to us on 03000 65 3000.
“We have not had any reports of sabotage in this area, but we will look into the matter.”
