The Iskar is, with a length of 368 km, the longest river that runs solely in Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, and a tributary of the Danube

Danube

The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....

.

The Iskar is formed by three rivers, the Cherni (black) Iskar, Beli (white) Iskar and Levi (left) Iskar (known under the collective name Iskrove), with the source being accepted to be the Prav (straight) Iskar, a tributary of the Cherni Iskar. After descending from the north slopes of Rila

Rila

Rila is a mountain range in southwestern Bulgaria and the highest mountain range of Bulgaria and the Balkans, with its highest peak being Musala at 2,925 m...

, it fills the Iskar Reservoir

Iskar Reservoir

The Iskar Reservoir is the largest reservoir in Bulgaria. It is situated on the Iskar River and provides 2/3 of the water for the capital Sofia, also being used for producing hydroelectricity....

—the largest in Bulgaria and the Lake Pancharevo

Lake Pancharevo

Lake Pancharevo is an artificial lake in western Bulgaria, at the end of the Pancharevo Gorge of the Iskar River, located at 600 m above sea level between the Vitosha and Lozenska mountains...

. The river runs near Sofia

Sofia

Sofia is the capital and largest city of Bulgaria and the 12th largest city in the European Union with a population of 1.27 million people. It is located in western Bulgaria, at the foot of Mount Vitosha and approximately at the centre of the Balkan Peninsula.Prehistoric settlements were excavated...

 and passes through a rocky gorge in the Balkan Mountains

Balkan Mountains

The Balkan mountain range is a mountain range in the eastern part of the Balkan Peninsula. The Balkan range runs 560 km from the Vrashka Chuka Peak on the border between Bulgaria and eastern Serbia eastward through central Bulgaria to Cape Emine on the Black Sea...

. It flows into the Danube near the village of Gigen

Gigen

Gigen is a village in northern Bulgaria, part of Gulyantsi Municipality, Pleven Province. It is located near to the Danube River, close to the place where the Iskar River empties into it, opposite the Romanian town of Corabia....

 in Pleven Province

Pleven Province

Pleven Province is a province located in central northern Bulgaria, bordering the Danube river, Romania and the Bulgarian provinces of Vratsa, Veliko Tarnovo and Lovech. It is divided into 11 subdivisions, called municipalities, that embrace a territory of 4,333.54 km² with a population, as...

. The Iskar is the only river to take its source from southern Bulgaria and cross the Balkan Mountains to flow into the Danube.
The Iskar flows through seven provinces of Bulgaria: the capital city of Sofia

Sofia

Sofia is the capital and largest city of Bulgaria and the 12th largest city in the European Union with a population of 1.27 million people. It is located in western Bulgaria, at the foot of Mount Vitosha and approximately at the centre of the Balkan Peninsula.Prehistoric settlements were excavated...

, Sofia Province

Sofia Province

Sofia Province is a province of Bulgaria. The province does not include Sofia in its territories, but Sofia however remains its administrative center...

, Pernik Province

Pernik Province

-Religion:Religious adherence in the province according to 2001 census:-Ethnic groups:Ethnic groups in the province according to 2001 census:145 642 Bulgarians ,3 035 Roma  and 1155 others and unspecified .-Economy:...

, Vratsa Province

Vratsa Province

Vratsa Province , former name Vratsa okrug) is a Bulgarian province located in the northwestern part of the country, between Danube river in the north and Stara Planina mountain in the south. It is named after its main town - Vratsa...

, Pleven Province

Pleven Province

Pleven Province is a province located in central northern Bulgaria, bordering the Danube river, Romania and the Bulgarian provinces of Vratsa, Veliko Tarnovo and Lovech. It is divided into 11 subdivisions, called municipalities, that embrace a territory of 4,333.54 km² with a population, as...

 and Lovech Province

Lovech Province

Lovech Province is one of the 28 provinces of Bulgaria, lying at the northern centre of the country. It is named after its main city - Lovech. As of December 2009, the population of the area is 151,153.-Municipalities:...

. This is the main source of water for Sofiyskavoda, the water and sewarage company in Sofia.

In terms of geology, the Iskar is the oldest river in the Balkans

Balkans

The Balkans is a geopolitical and cultural region of southeastern Europe...

 and also the only one to have preserved its original direction despite the significant geological changes in later stages.

Honour

Iskar Glacier

Iskar Glacier

Iskar Glacier is a glacier in Livingston Island, draining the north slopes of the Tangra Mountains between Helmet Peak to the west and Delchev Peak to the east...

 on Livingston Island in the South Shetland Islands

South Shetland Islands

The South Shetland Islands are a group of Antarctic islands, lying about north of the Antarctic Peninsula, with a total area of . By the Antarctic Treaty of 1959, the Islands' sovereignty is neither recognized nor disputed by the signatories and they are free for use by any signatory for...

, Antarctica is named after Iskar River.