A country of South Asia in the Himalaya Mountains between India and southwest China. Site of a flourishing civilization by the 6th century BC , the region was later divided into principalities, one of which, Gurkha, became dominant in the 18th century. Gurkha's expansion into northern India led to border wars with Great Britain. A 1923 treaty affirmed Nepal's full sovereignty, and a constitutional monarchy was established in 1951. Kathmandu is the capital and the largest city.