Kullu is a district in Himachal Pradesh, India. It borders Shimla district to the south, Mandi and Kangra districts to the west, and the Lahaul and Spiti district to the north and east. The largest valley in this mountainous district is the Kullu Valley. The Kullu valley follows the course of the Beas River, and ranges from an elevation of 833m above sea level at Aut to 3330m above sea level at the Atal Tunnel South Portal, below the Rohtang Pass. The town of Kullu, or simply Kullu, located on the right side of the Beas River, serves as the administrative headquarters of the Kullu district. The Kullu district also incorporates several riverine tributary valleys of the Beas, including those of the Parvati, Sainj, and Tirthan rivers, and thus some regions somewhat distant from the Kullu valley. The economy of the district relies mainly on horticulture, agriculture, tourism, and traditional handicrafts. History The ancient seat of the kings of the kingdom of Kullu was the Naggar Castle, about 12 km north of the present-day town of Kullu, and was thought to have been built in the late 15th century. Raja Jagat Singh (who ruled Kullu between 1637–72) moved the capital in the middle of the 17th century from Naggar to Sultanpur, within today's Kullu town. Kullu ended being an independent kingdom upon the invasion by Maharaja Ranjit Singh in 1839. Following, in turn, the takeover of the Sikh Empire by the British Empire, Kullu was ceded by the Sikhs to the British in 1846, whereupon it became a tehsil of the British-administered Kangra district (in turn a part of the Punjab Province, British India). The head of Kullu's royal family had been granted the Waziri Rupi by the Sikh emperor along with the title 'Rai', and this continued throughout the British period. Naggar Castle was exchanged by Raja Gyan Singh of Kullu for a rifle with Major Hay, the first Assistant Commissioner of the then-newly acquired British territory of Kullu. The Rupi Palace in Sultanpur is still used as home by the descendants of Kullu's royal family. Upon the Independence of India, until 1960, Lahaul and Spiti continued being parts of the Kullu tehsil, as had also been the case during the British rule. In 1960, Lahaul and Spiti became a separate district. Kullu became a district of Punjab in 1963, and on November 1,1966, it became a district of