South West China, the exotic area, home to many minority ethnic groups. Like other Western areas, it is less prosperous than the coastal regions.
Much of the terrain is quite mountainous. Tibet and Yunnan have many very high mountains; the world's highest (Mount Everest) is on the Tibet/Nepal border. Guizhou and Guangxi have smaller mountains, karst limestone terrain, with fantastically shaped hills, terraced rice fields, and many caves.
The Wikitravel itinerary Overland Kunming to Hong Kong covers travel through this region.