The abandoned city of Harlaa located 120 km from the Red Sea coast in eastern Ethiopia was occupied between the 7th-15th centuries AD, and has provided significant new information on the role of Ethiopia in the medieval Islamic World. Harlaa was an important gateway for Islam, and an entrepot supplying maritime and land-based trade networks, based on industries such as mining, and jewelry production in dedicated workshops. The wealth of Harlaa appears to have been immense with elaborate stone-built architecture, and material such as glass vessels, glass and semi-precious stone beads, copper and silver coins, Chinese and Middle Eastern ceramics, and shell, imported from India, Sri Lanka, Egypt, Iran, Central Asia, and Yemen. Burial, dietary, and epigraphic evidence indicate a cosmopolitan community, Muslim, and non-Muslim, and one that was instrumental in the gradual Islamisation of eastern Ethiopia, and which also seems to have been responsible for the founding of the extant city of Harar. In the absence of historical sources, archaeology is indicating that rather than being peripheral, medieval eastern Ethiopia had an important role within the Islamic world.