Located at the crossroads between Africa and Asia, Damascus is considered to be among the oldest continuous human habitations in the world. Excavations at Tell Ramad on the outskirts of the city indicate that Damascus was inhabited as early as 10,000 BC. The city has some 125 significant structures and monuments from different periods of its history – Hellenistic, Roman, Byzantine and Islamic. One of the most spectacular is the 8th-century Great Mosque of the Umayyads, built on the site of an Assyrian church. In spite of Islam’s dominant influence on Damascus, Roman and Byzantine influences can be seen everywhere. Indeed, the city’s current layout is based on a traditional Roman plan with all of the streets oriented either north-south or east-west. The remains of the Temple of Jupiter, various gates, and an impressive section of the Roman city walls also attest to the city’s Roman past. Although, the Citadel, some mosques, and tombs survive from the Middle Ages, most of the remaining parts of the old city date to the Ottoman conquest of the mid-1500s.