Northern Thrace or North Thrace (Bulgarian: Северна Тракия, Severna Trakiya) (as opposed to Western Thrace and East Thrace to the south) constitutes the northern and the largest part of the historical region of Thrace. Bulgarian Thrace is located in Southern Bulgaria and refers to the whole territory south of the Balkan Mountains and east of the Mesta River; to the Greek and Turkish borders in south and to the Black Sea in east. It encompasses Sredna Gora, the Upper Thracian Plain and 90% of the Rhodopes. The climate differs from continental to transitional continental and mountainous. The highest temperature recorded in Bulgaria occurred here: it was 45.2 °C at Sadovo in 1916. Important rivers are the Maritsa and its tributaries. Important cities include Plovdiv, Burgas, Stara Zagora, Sliven, Haskovo, Yambol, Pazardzhik, Asenovgrad, Kardzhali, Dimitrovgrad, Kazanlak and Smolyan. Northern Thrace has an area of 42,073 km².