Bulgaria
Bulgaria, officially the Republic of Bulgaria, is a country in Southeast Europe. It is bordered by Romania to the north, Serbia and North Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east. The capital and largest city is Sofia; other major cities are Plovdiv, Varna and Burgas. With a territory of 110,994 square kilometres, Bulgaria is Europe's sixteenth-largest country. One of the earliest societies in the lands of modern-day Bulgaria was the Neolithic Karanovo culture, which dates back to 6,500 BC. In the 6th to 3rd century BC the region was a battleground for ancient Thracians, Persians, Celts and Macedonians; stability came when the Roman Empire conquered the region in AD 45. Around the 6th century, some of these territories were settled by the early Slavs. They were invaded by small number of warlike Bulgars in the late 7th century who subdued the Slavs and founded there the First Bulgarian Empire in AD 681.