Treasure Seekers: Tibet's Hidden Kingdom: Tibet at the end of the nineteenth century was one of the last great unexplored regions of the world - a mysterious kingdom on the rooftop of the world. As it became aware of the colonial designs of European power on central Asia, Tibet expelled westerners and closed its frontiers. As its isolation deepened, so did Tibet's allure and mystique. European and North American 'gentlemen' explorers, government agents, missionaries and adventurers had managed to penetrate nearly every other corner of Africa and Asia.