Iskar Gorge

It is the chief pass through the Balkans, which otherwise cross northern Bulgaria in a solid line.

[1] The pass connects the capital of Sofia with other major cities in the country, such as Mezdra.

There is a road and a railway through the pass, following the course of the Iskar River.

[1] The canyon walls are made of limestone and sandstone, which was carved down by the Iskar over thousands of years, resulting in rugged crags and towers throughout.

[1] At one point, the walls are nearly 300 metres (980 ft) tall.