Niš (pronounced as Nish) is the largest city in southern Serbia and the third-largest city in the country (after Belgrade and Novi Sad). Niš has around 300.000 inhabitants. The city covers an area of about 597 square kilometres, including the urban area, the Niška Banja (Spa of Niš) and 68 suburbs. Niš is the administrative centre of the Nišava District. It is one of the oldest cities in the Balkans and has been considered from ancient times a gateway between the East and the West. Niš is also notable as the birthplace of Constantine the Great, the first Christian Roman Emperor and the founder of Constantinople, as well as two other Roman emperors, Constantius III and Justin I. It is home to one of Serbia’s oldest Christian churches dating to the 4th century in the suburb of Mediana. There are about 30,000 university students at the University of Niš, which comprises 13 faculties. Niš is also one of the most important industrial centres in Serbia, a centre of the electronics industry, the industry of mechanical engineering, the textile industry and the tobacco industry, but after everything that happened in the country, it is economically still weak. Constantine the Great Airport is an international airport located in Niš.