Niš (; , ; names in other languages) is the third largest city in Serbia and the administrative center of the Nišava District. It is located in southern part of Serbia. , the city proper has a population of 183,164, while its administrative area (City of Niš) has a population of 260,237 inhabitants. Several Roman emperors were born in Niš or used it as a residence: Constantine the Great, the first Christian emperor and the founder of Constantinople, Constantius III, Constans, Vetranio, Julian, Valentinian I, Valens; and Justin I. Emperor Claudius Gothicus decisively defeated the Goths at the Battle of Naissus (present-day Niš). Later playing a prominent role in the history of the Byzantine Empire, the city's past would earn it the nickname Imperial City. After about 400 years of Ottoman rule, the city was liberated in 1878 and became part of the Principality of Serbia, though not without great bloodshed—remnants of which can be found throughout the city. Today, Niš is one of the most important economic centers in Serbia, especially in the electronics, mechanical engineering, textile, and tobacco industries. Constantine the Great Airport is Niš's international airport. The city is also the seat of the University of Niš, the Eparchy of Niš and the Command of Serbian Army. In 2013, the city was host to the celebration of 1700 years of Constantine's Edict of Milan. Name The town was named after the Nišava River, which flows through the city. It was first named Navissos by Celtic tribes in the 3rd century BC. From this term comes the Latin Naissus, the Greek Nysos and the Slavic Niš. Other variations include: Νάϊσσος, Ναϊσσός (Naissos), Naessus, urbs Naisitana, Navissus, Navissum, Ναϊσσούπολις (Naissoupolis). In Old Serbian, the town was known as Niš (written Нишь and Ньшь). The name is historically rendered as Nish or Nissa in English. Niš evolved from the toponym attested in Ancient Greek as ΝΑΙΣΣΟΣ (Naissos), which achieved its present form via phonetic changes in Proto-Albanian and thereafter the placename entered Slavic. Nish might indicate that Proto-Albanian was spoken in the region in pre-Slavic antiquity. Per Eric P. Hamp the name of Niš is clearly Albanian in shape. According to Ismajli (2015), when this settlement happened is a matter of debate, as Proto-Albanians might have moved relatively late in antiquity in the area which might have been an eastern expansion of Proto-Albanian settlement as no other toponyms known in