Balkan Mountains
The Balkan mountain range (, , known locally also as Stara planina) is a mountain range in the eastern part of the Balkan Peninsula in Southeastern Europe. The range is conventionally taken to begin at the peak of Vrashka Chuka on the border betw ...
(Stara Planina) in
Bulgaria
Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedon ...
. It is the chief pass through the Balkans, which otherwise cross northern Bulgaria in a solid line. The pass connects the capital of
Sofia
Sofia ( ; bg, София, Sofiya, ) is the capital and largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain in the western parts of the country. The city is built west of the Iskar river, and ha ...
with other major cities in the country, such as
Mezdra
Mezdra ( bg, Мездра ) is a town in northwestern Bulgaria, part of Vratsa Province. It is located on the left bank of the Iskar River just north of its gorge through the Balkan Mountains.
History
Although the area around it has been inhabite ...
. There is a road and a railway through the pass, following the course of the
Iskar River
The Iskar ( bg, Искър, ; la, Oescus) is a right tributary of the Danube. With a length of 368 km it is the longest river that runs entirely within Bulgaria.
The canyon walls are made of
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
and
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
, which was carved down by the Iskar over thousands of years, resulting in rugged crags and towers throughout. At one point, the walls are nearly tall.