Dilijan National Park covers roughly 240 square kilometres of forested mountains east of the town. It is often called the lungs of Armenia — a reference both to the clean air and to the rarity of intact forest at this scale anywhere in the country. The park's hiking trails range from easy walks through beech forest to multi-day traverses along the Transcaucasian Trail, a long-distance route that runs from the Black Sea to the Caspian.
The park's most visited spot is Parz Lake (Lake Clear), a small mountain lake surrounded by forest about 6 kilometres from Dilijan, with a zip-line and rowboats for hire. The trails from Dilijan town into the park begin just above the old quarter and take you quickly into genuine wilderness. Bears, wolves, and lynx inhabit the park, though sightings are rare. The park visitor centre in Dilijan can advise on trail conditions and guided walks.