<span>Two factors that limited China's contact with outsiders were natural barriers that separated the main landmass of China from other areas and the comparatively long distances one had to travel to reach main population centers. Features such as the Himalayan Mountains, the Tibetan Plateau and the Gobi Desert made travel across the borders and within the country difficult, and the sheer size of the country and the distance required to travel to any major commercial or population centers made the effort unprofitable at best.</span>