The spread of Islam in the early medieval era of Somalia's history brought Islamic architectural influences from Arabia and Persia, which stimulated a shift from drystone and other related materials in construction to coral stone, sundried bricks, and the widespread use of limestone in Somali architecture. Many of the new architectural designs such as mosques were built on the ruins of older structures, a practice that would continue over and over again throughout the following centuries. Concordant with the ancient presence of Islam in the Horn of Africa region, mosques in Somalia are some of the oldest on the entire continent. One architectural feature that made Somali mosques distinct from other mosques in Africa were minarets.