A mountain biker collapsed and died while riding the Marin Trail near Betws-y-Coed, North Wales, on Saturday.
The 54-year-old man, who has not been named, suffered chest pains while climbing a steep slope with his brother and a friend. An ambulance was called but could not reach him.
Paramedics eventually made it to the scene on foot, where they spent over an hour trying to revive the Flintshire man, but their efforts proved fruitless.
A spokesman for Welsh Ambulance Services NHS Trust said: "We were called at 4.08pm to an incident where a man had collapsed with chest pains while cycling on a forest track. One ambulance attended but due to the rough terrain the crew had to go on foot to reach the casualty. They were assisted by Ogwen Valley Mountain Rescue, but despite attempts to revive the patient he was declared deceased at scene."
The 17-mile, red-graded Marin trail is known for its long fireroad climbs and is a favourite with hardcore cross-country riders.