Sofia was established as a Thracian settlement around the 8th century BCE and has since developed into a major world city and the capital of Bulgaria, due in part to its central position in the Balkans. Today it is home to attractions like the 6th century Church of St. Sofia and 15th century Banya Bashi mosque. During its long history, the city passed through the hands of the Roman, Byzantine, and Ottoman empires. After nearly 500 years of Turkish rule, Sofia was liberated by what country? Discuss