The Dospat is a river in the Western Rhodope Mountains

Rhodope Mountains

The Rhodopes are a mountain range in Southeastern Europe, with over 83% of its area in southern Bulgaria and the remainder in Greece. Its highest peak, Golyam Perelik , is the seventh highest Bulgarian mountain...

, the most important tributary of the Mesta

Mesta River

The Nestos or Mesta , formerly the Mesta Karasu , is a river in Bulgaria and Greece. It rises in the Rila Mountains and flows into the Aegean Sea near the island of Thasos. It plunges down towering canyons toward the Aegean Sea through mostly metamorphic formations...

.

It takes its source from 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...

, from the 1643-metre-high Rozov vrah ("Rose Peak") and flows southeast until Dospat Dam, after which it makes a turn southwest to continue generally to the south and flow into the Mesta as a left tributary on Greek

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

 territory just south of the Greek-Bulgarian border. The river has a drainage basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

of 633.5 km²