Sofia, Bulgaria is the largest city in the country, and the capital of the Republic of Bulgaria. It has a population of approximately 1,400,000 people. Sofia is located in western Bulgaria, and is the administrative, cultural and industrial center of the country. Sofia is one of the oldest capital cities in Europe. It has several historic landmarks, including one of the UNESCO World Heritage protected sites. Other attractions include the National Opera and Ballet, The National Theater, one of the world's largest Orthodox churches, and early Byzantine churches. It is also has the home of an outdoor book market, and the NDK, which is southeastern Europe's largest cultural and congressional center. There are 16 universities in the city, including Sofia University which was founded in 1888.