Palmyra, also known as Tadmor, is an ancient city located in Homs Governorate, Syria. The city was first documented in the early second millennium BC. The city became prosperous as a result of trade caravans; the Palmyrenes became well-known as merchants who founded colonies along the Silk Road and operated throughout the Roman Empire. Palmyra reached its peak of prosperity during the Palmyrene Empire during the reign of Queen Zenobia between 270 and 273 AD. Palmyra was inscribed in the UNESCO World Heritage Site in 1980.