The Khun Than mountain range of the Doi Khun Than National Park forms a natural boundary between Lamphun and Lampang provinces.
Located in the mountains of northern Thailand, Doi (mountain) Khuntan national park is home to many interesting species of flora and fauna as well as historical places. One of its distinguished feature is the Thailand's longest railroad tunnel (Khun Tan tunnel), which is 1,352 meters long. Doi Khuntan National Park contains the mountains straddling Lamphun and Lampang provinces. Established in 1975, it is the14th national park in Thailand.
The name of this park has significant meaning. "Doi" translates to mountain in Northern Thai, while "Khun tan" refers to the numerous streams flowing down from the mountain.

Khun Tan tunnel
Construction of the tunnel at Khuntan, which was cut through solid granitee bedrock, began in 1918. Khuntan tunnel was nicknamed the "cemetery of laborers" as it is said that over 1,000 workers died while constructing the tunnel due to suffocation, accidents, malaria, tigers and fighting amongst themselves. It is said that the workers were opium addicts (how they became addicts is unknown) who agreed to work because they were given opium in addition to the wages.

Forests
The forests of Doi Khuntan have changed dramatically in the past century due to human disturbance. The forests can be divided into three types according to the elevations.
The lowland elevations (325 - 850 meters). Originally a teak forest, the lowland elevation is composed of a degraded mixed bamboo deciduous forest and deciduous Dipterocarp - oak forest. The middle elevations (850 - 1,000 meters). This is a transitional area where the lowland deciduous forest and upland evergreen - pine forest mix to from the mixed evergreen and deciduous forest. Two species of pine trees in Thailand: a two-needle pine (Pinus merkusii) and three-needle pine (P. kersiya) are found here. The upland Eeevations (1,000 - 1,373 meters). The forest in this range is composed mostly of evergreen hardwood trees and a minority of pine (Pinus merkusii) forming an evergreen - pine forest. Much of the forest and watershed on the west side of the national park have been distrubed; however, healthy conditions are seen on the eastern side.
In addition, Doi Khuntan offers year-round viewing of wild-flowers such as orchids, gingers and lilies. Doi Khuntan is botanically very diverse. Numerous edible plants and fungi are found in the park.
Some wildlife still exists in Doi Khuntan, including the Siamese hare, porcupine, wild chicken, wild boar and weasel, a variety of birds, reptiles, spiders and insects. The effects of hunting, logging, frequent fires and human encroachment have greatly reduced their numbers. In the past, gibbons, tiger, elephants, bears, wild cattle, serow, slow loris, barking deer and many other species were also residents of Doi Khuntan.
In addition to hiking the trail (approximately 8 km from Khun Tan train station near the tunnel) to the summit, people can also visit the four waterfalls. Daht Moei waterfall is easily accessible and is located on the 6 km round trip hiking route from the park's headquarters. Mae Prai waterfall is more magnificent and is accessible by a 12 km round trip trail from the park station at Mae Prai in Chat district, Lampang province.