Throughout most of the Islamic period (7th century and after), caravanserais were a common type of structure both in the rural countryside and in dense urban centers across the Middle East, North Africa, and Ottoman Europe. A number of 12th to 13th-century caravanserais or "han"s were built throughout the Seljuk Empire, many examples of which have survived across Turkey today (e.g. the large Sultan Han in Aksaray Province) as well as in Iran (e.g. the Ribat-i Sharaf in Khorasan). Urban versions of caravanserais also became important centers of economic activity in cities across these different regions of the Muslim world, often concentrated near the main "souq" areas, with many examples still standing in the historic areas of Damascus, Aleppo, Cairo, Istanbul, Fes, etc.