The greatest contribution of the Islamic hospitals was the structure itself and how it functioned in Islamic culture. The first documented general hospital (hospitals that treated a multitude of pathologies, including mental illness) arose in Baghdad, in 805, built by vizier to the caliph, Harun al-Rashid. Although not much is known about this hospital due to poor documentation, the system of the general hospital itself set forth an example for the many other hospitals to come. Soon after, 34 new hospitals were built throughout the Islamic world with the number increasing annually. Islamic hospitals were even the first to specialize in treating convicts as the prison population was continually increasing.