Answer: Roman precinct walls
Explanation: The Great Mosque of Damascus was built by the Umayyad Caliph Al Walid. The Caliph selected a site that had previously been a temple, first to Hadad and then Jupiter Dolichhenus. The temple had a Roman design and when Al Walid demolished the temple, he left the Roman Precinct walls which gives it its distinct Greco-Roman architecture look. The walls formed the entry to the mosque and are still present in the mosque.