Geologically, the gorge is cut in strong limestones with a complex and varied structure, formed about 200 million years ago in a sea basin.

[1] Up to the middle section, the walls of the Tran Gorge are vertical, and their width does not exceed 10–15 m. It was formed over millions of years by an erosion process from the impact of the river, which little by little made its way through the rock.

[1][5] The gorge is situated in a forested area of the small Ruy mountain range, just north of the Znepole valley, and is home to diverse flora and fauna.

[3] A 200 m tunnel passes under Zhilav Kamak, excavated in the early XX century for a railway line between the towns of Tran and Tsaribrod, when the latter belonged to Bulgaria.

of the 19th century writer and initiator of the tourist movement in Bulgaria Aleko Konstantinov: "Do you see those jagged gray giant rocks glistening in the sun?

"[4] The surroundings of the gorge are depicted in the 1913 painting Erma River near Tran of the Bulgarian landscape painter Nikola Petrov, kept in the National Art Gallery, which is considered to recall the works of Edgar Degas and Georges Seurat.