tons. Marco Polo, who sailed from China to Persia on his return home, described the Mongol ships as large four-masted junks with up to three hundred crewmen and as many as sixty cabins for merchants carrying various wares. According to Ibn Battuta, some of the ships even carried plants growing in wooden tubs in order to supply fresh food for the sailors. Khubilai Khan promoted the building of ever larger seagoing junks to carry heavy loads of cargo and ports to handle them. They improved the use of the compass in navigation and learned to produce more accurate nautical charts. The route from the port of Zaytun in southern China to Hormuz in the Persian Gulf became the main sea link between the Far East and the Middle East, and was used by both Marco Polo and Ibn Battuta, among others.