At it's zenith, the Mongol Empire encompassed a substantial portion of the Eurasian landmass, including China, the Middle East, the Balkans, and a substantial portion of Russia and Siberia. Japan, India, and Indochina were not part of the Empire. A planned invasion of Japan failed when a huge Mongol fleet, the largest until World War II, was destroyed by a typhoon, which the Japanese called a "divine wind,' or Kamakaze.Because the Mongols were horsemen from the steppes, their method of warfare did not work well in tropical rain forests, so they did not conquer the deep south.
The Mongols encouraged regular communication within their empire. Diplomats, missionaries, etc. were allowed to travel freely. They encouraged trade, and were largely responsible for the beginning of large scale trade between Western Europe and China. They policed the silk roads heavily, which further enhanced trade and cultural exchange between East and West.