Loei (Thai: ???) Province is located in Thailand's upper North-East. Neighboring provinces are (from east clockwise) Nong Khai, Udon Thani, Nongbua Lamphu, Khon Kaen, Phetchabun, Phitsanulok. In the north it borders Xaignabouli and Vientiane Provinces of Laos. The province is covered with low mountains, while the capital Loei is located in a fertile basin. The Loei River, which flows through the province, is a tributary of the Mekong which, together with the smaller Hueang River, forms the northern boundary of the province with neighboring Laos. Although temperatures in the hot season (April-May) can be more than 40 degrees Celsius, the province is the only one in Thailand where temperatures regularly drops below freezing at night in the cold season (December-January). Loei is rich in national parks, including especially Phu Kradung, Phu Ruea, Phu Suan Sai (also known as Na Haeo) and Phu Luang Wildlife Sanctuary. In 1853 King Mongkut (Rama IV) founded the city of Loei to administer the increasing population in what was then a remote area. In 1907 the province was created by King Chulalongkorn (Rama V). The province is also famous for the Phi Ta Khon festival held at Dansai during the 6th lunar month to make merit and honour the spirits of the ancestors - a colourful mix of Buddhism and spirit worship. The symbol of the province is the stupa (chedi) at Phra That Si Song Rak in Dan Sai, which was built in 1560 by King Maha Chakrapat of Ayutthaya and King Chai Chetha of Lan Xang as a symbol of friendship between the Siamese and Lao kingdoms.