The Abbasid era renewed the Afro-Eurasian trading system and the western commercial system. Merchants used dhows, sailing vessels that allowed them to bring goods to not only the whole empire but to the whole world which made them very wealthy. Merchants also took charge of the luxurious items for the elites in the society. The enormous revenues that trading brought in was invested into new land, profitable businesses, and lavish homes. Furthermore, the money from trading also went to building mosques, schools and helping the poor. The amount of hospitals built in the Abbasid empire and the excellence of their doctors surpassed everyone during that time period. The development of cities encouraged the growth of a wide range of new industries. Privately-owned industries increased the production of furniture, carpets, and leather. The countryside was owned by the upper-class who hired peasants or slaves to work the land. Trade greatly influenced the development of the Abbasid