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Sremska Mitrovica is a city and municipality located in the Vojvodina province, Serbia, on the left bank of the Sava river. It is the administrative centre of the Srem District of Serbia.
Once a capital of the Roman Empire during the Tetrarchy, the city was referred to as the glorious mother of cities.[3] Likewise, ten Roman Emperors were born in or near this city, Emperors Herennius Etruscus (251), Hostilian (251), Decius Traian (249-251), Claudius II (268-270), Quintillus (270), Aurelian (270-275), Probus (276-282), Maximianus Herculius (285-310), Constantius II (337-361) and Gratian (367-383).

The Sava is a river in Southeast Europe, a right side tributary of the Danube river discharging in Belgrade. It is 990 kilometres (615 miles) long, including 45-kilometre (28 mi) Sava Dolinka headwater rising in Zelenci Pools near Podkoren, Slovenia - draining the second largest catchment among Danube tributaries after Tisza and covering 97,713 square kilometres (37,727 square miles) of surface area. It flows through Slovenia, Croatia, along the northern border of Bosnia-Herzegovina, and through Serbia. Its central part is a natural border of Bosnia-Herzegovina and Croatia. Sava is considered to be the northern border of the Balkan Peninsula.
It belongs to the Black Sea drainage basin and, together with Sava Dolinka, represents the third longest Danube's tributary, as well as the richest with water, by far. It drains a significant portion of the Dinaric Alps region, through significant tributaries of Drina, Bosna, Kupa, Una, Vrbas, Lonja, Kolubara, Bosut and Krka. Sava is one of the longest rivers in Europe and among handful European rivers that long, that do not drain directly into a sea.