The Erythropotamos Luda reka 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...

  is a river that flows from south of Mega Dereio

Mega Dereio

Mega Dereio is a village in the northcentral part of the Evros Prefecture in Greece. It is part of the municipal unit of Orfeas. The location is near the heart of the prefectural mainland and is centrally located between the Bulgarian and the Turkish borders as well as the Evros River. Its 2001...

 next to the Ivaylovgrad

Ivaylovgrad

Ivaylovgrad is a town in Haskovo Province in the very south-east of Bulgaria set near the river Arda in the easternmost part of the Rhodope Mountains. It is the administrative centre of the homonymous Ivaylovgrad Municipality...

 municipality in southern 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 northern Greek Thrace

Western Thrace

Western Thrace or simply Thrace is a geographic and historical region of Greece, located between the Nestos and Evros rivers in the northeast of the country. Together with the regions of Macedonia and Epirus, it is often referred to informally as northern Greece...

 entirely in the Evros Prefecture

Evros Prefecture

Evros is one of the regional units of Greece. It is part of the region of East Macedonia and Thrace. Its name is derived from the river Evros, which appears to have been a Thracian hydronym. Evros is the northernmost regional unit. It borders Turkey to the east, across the river Evros, and it...

. Its Turkish name was Küzüldeli Su. It flows into the Maritsa

Maritsa

The Maritsa or Evros , ) is, with a length of 480 km, the longest river that runs solely in the interior of the Balkans. It has its origin in the Rila Mountains in Western Bulgaria, flowing southeast between the Balkan and Rhodope Mountains, past Plovdiv and Parvomay to Edirne, Turkey...

 (Evros River) near Didymoteicho

Didymoteicho

Didymóteicho is a town located in the eastern part of the Evros peripheral unit of Thrace, Greece. It is the seat of the municipality of the same name. The town sits on a plain and located south east of Svilengrad, south of Edirne, Turkey and Orestiada, west of Uzunköprü, about 20 km north...

.

The river begins in Greece in the western Evros Prefecture

Evros Prefecture

Evros is one of the regional units of Greece. It is part of the region of East Macedonia and Thrace. Its name is derived from the river Evros, which appears to have been a Thracian hydronym. Evros is the northernmost regional unit. It borders Turkey to the east, across the river Evros, and it...

, it passes into Mega Dereio

Mega Dereio

Mega Dereio is a village in the northcentral part of the Evros Prefecture in Greece. It is part of the municipal unit of Orfeas. The location is near the heart of the prefectural mainland and is centrally located between the Bulgarian and the Turkish borders as well as the Evros River. Its 2001...

 and through a remote road into Ivaylovgrad municipality 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...

, through the villages of Gorno Lukovo

Gorno Lukovo

Gorno Lukovo is a village in the municipality of Ivaylovgrad, in Haskovo Province, in southern Bulgaria.-References:...

 and Dolno Lukovo

Dolno Lukovo

Dolno Lukovo is a village in the municipality of Ivaylovgrad, in Haskovo Province, in southern Bulgaria.-References:...

 (Upper and Lower Lukovo) and Siv Kladenets

Siv Kladenets

Siv Kladenets is a village in the municipality of Ivaylovgrad, in Haskovo Province, in southern Bulgaria.-References:...

 with a tributary known as the Byala reka

Byala reka

Byala reka is a river in the Rhodope Mountains in Southern Bulgaria, the longest tributary of Luda reka .The river rises near the village of Chernichevo, close to the Greek border then flows in a general eastern direction until it flows into Luda reka near Siv Kladenets exactly on the Greek...

 ("white river"). The river reenters Greece and flows north of Protoklissi

Protoklissi

Protokklisi is a village in the northcentral part of the Evros Prefecture in Greece. Protoklissi is in the municipal unit of Orfeas. The location is near the heart of the prefectural mainland and is centrally located between the Bulgarian and the Turkish borders as well as the Evros River...

, the nearby villages include Paliouri and Sitochori

Sitochori, Evros

Sitochori is a village in the western part of the municipality of Didymoteicho in the northcentral Evros Prefecture. Sitochori is located southwest of Orestiada, about 10 km west of Didymoteicho and Turkey, north of Soufli, north-northeast of Alexandroupoli and east of Bulgaria...

.