Erma River Gorge (second name - Trynskoe Gorge) is located near the town of Tran and recognized as one of the most beautiful sights of nature in this region of the country. The gorge depth of nearly 100 m and a width at the narrowest portion of up to 5 m. High (150-200 m) is surrounded by steep cliffs on both sides of the river.

Special ecotrail, originating in the southern part of the canyon, paved for tourists and nature lovers. The route length of 13 km lies on a wooden bridge across the river Erma, as well as through a tunnel, located in the rock, then down the wooden bridge 35 meters long, and then starts climbing on the rock, located on the west valley. The most interesting objects of this route - Erma river gorge and Yablanishka. The view from ecotrail, striking impressiveness rock formations in the river gorges, spectacular waterfalls and foaming rapids. Erma River Gorge was formed by the erosive effects of the river for thousands of years it has cut limestone. Over a hundred years ago, a great writer Aleko Konstantinov visited Bulgaria is a place that so impressed him that he exclaimed: "What is Switzerland? ".

This gorge landmark nature of the official announcement by the order of July 1961 in order to preserve the unique rock formations. In addition, there is the amazing beauty of wildlife. In a small area there are about a dozen species of shrubs, trees and grasses. Some species are incredibly beautiful, such as the lilacs blooming in May, September and October, or sumac, and, of course, unique iris Reichenbach, which is found only in the Balkans, it can be seen only in June.

Impressive and a variety of bird species live here such interesting representatives, as the white stork, honey buzzard, Montagu's harrier, etc. Mammals can watch otters, small and large horseshoe bats, wolves, lynx, etc. There are here and amphibians: southern crested newt, fire-bellied toads and other yellow-bellied.