The Upper Thracian Plain constitutes the northern part of the historical region of Thrace

Thrace

Thrace is a historical and geographic area in southeast Europe. As a geographical concept, Thrace designates a region bounded by the Balkan Mountains on the north, Rhodope Mountains and the Aegean Sea on the south, and by the Black Sea and the Sea of Marmara on the east...

. It is located 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...

, between the Sredna Gora

Sredna Gora

Sredna Gora is a mountain range in central Bulgaria, situated south of and parallel to Balkan mountain range and extending from the river Iskar to the west and the elbow of Tundzha north of Yambol to the east. Sredna Gora is 285 km long, reaching 50 km at its greatest width...

 mountains to the north and west; the Rhodopes, Sakar

Sakar

Sakar is a mountain in southeastern Bulgaria, between the rivers Maritsa, Tundzha, Sokolitsa and Sazliyka and close to the borders with Greece and Turkey. The mountain's highest peak is Vishegrad at 856 m....

 and Strandzha

Strandzha

Strandzha is a mountain massif in southeastern Bulgaria and the European part of Turkey, in the southeastern part of the Balkans between the plains of Thrace to the west, the lowlands near Burgas to the north and the Black Sea to the east. Its highest peak is Mahya Dağı in Turkey, while the...

 to the south; and the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

 to the east. A fertile agricultural region, the Upper Thracian Plain proper has an area of 6032 square kilometres (2,329 sq mi) and an average elevation of 168 metres (551.2 ft). The plain is part of Northern Thrace

Northern Thrace

North Thrace or Northern Thrace constitutes the northern and the largest part of the historical region of Thrace...

 (Северна Тракия, Severna Trakiya). The climate is transitional continental. The highest temperature recorded in Bulgaria occurred here: it was 45.2 °C (113.4 °F) at Sadovo

Sadovo

Sadovo is a small town in the Plovdiv Province, central Bulgaria. The population is 2 551. Most of the people are employed in agriculture, which due to the fertile soils and the high levels of mechanisation is efficient and highly productive. Major crops are apples, tomatoes, peppers, wheat,...

 in 1916. The precipitation is 550 millimetres (21.7 in) a year. Important rivers are 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...

 and its tributaries, the Tundzha

Tundzha

The Tundzha is a river in Bulgaria and Turkey and the most significant tributary of the Maritsa, emptying into it on Turkish territory near Edirne....

, the Stryama

Stryama

The Stryama is a river in southern Bulgaria, an important left tributary of the Maritsa. The river is 110.1 km long and has a drainage basin of 2,853 km²....

, the Topolnitsa

Topolnitsa

The Topolnitsa is a river in southern Bulgaria, an important left tributary of the Maritsa. It takes its source from Bich Peak in Sredna Gora close to Koprivshtitsa; it is known as the Shirineyska in its upper course. Its average discharge is 55 m³/s and it is long; its drainage basin covers...

, and the Vacha

Vacha River

The Vacha is a river in south Bulgaria, one of the main right tributaries of the Maritsa. It is 105 km long and is formed by the confluence of the Shirokolashka reka and the Byunovska reka. The river passes through Krichim Dam and Vacha Dam that secure drinking water for Plovdiv and its plains...

.

Important cities include Plovdiv

Plovdiv

Plovdiv is the second-largest city in Bulgaria after Sofia with a population of 338,153 inhabitants according to Census 2011. Plovdiv's history spans some 6,000 years, with traces of a Neolithic settlement dating to roughly 4000 BC; it is one of the oldest cities in Europe...

, Burgas

Burgas

-History:During the rule of the Ancient Romans, near Burgas, Debeltum was established as a military colony for veterans by Vespasian. In the Middle Ages, a small fortress called Pyrgos was erected where Burgas is today and was most probably used as a watchtower...

, Stara Zagora

Stara Zagora

Stara Zagora is the sixth largest city in Bulgaria, and a nationally important economic center. Located in Southern Bulgaria, it is the administrative capital of the homonymous Stara Zagora Province...

, Pazardzhik

Pazardzhik

Pazardzhik is a city situated along the banks of the Maritsa river, Southern Bulgaria. It is the capital of Pazardzhik Province and centre for the homonymous Pazardzhik Municipality...

, Asenovgrad

Asenovgrad

Asenovgrad is a town in central southern Bulgaria, part of Plovdiv Province.-History:Asenovgrad was founded by the Thracians as Stenímachos around 300–400 BC. In 72 BC the city was captured by the troops of the Roman Empire as part of the Roman expansion towards the Black Sea. After a long period...

, Haskovo

Haskovo

Haskovo , is a city, an administrative centre of the homonymous Haskovo Province in southern Bulgaria, not far from the borders with Greece and Turkey. As of February 2011, it has a population of 74,843 inhabitants....

, Yambol

Yambol

Yambol is a city in southeastern Bulgaria, an administrative centre of Yambol Province. It lies on both banks of the Tundzha river in the historical region of Thrace. As of February 2011, the town has a population of 72,843 inhabitants. It is occasionally spelt 'Jambol'.The administrative centres...

 and Sliven

Sliven

Sliven is the eighth-largest city in Bulgaria and the administrative and industrial centre of Sliven Province and municipality. It is a relatively large town with 89,848 inhabitants, as of February 2011....

.