Four Ashoka Stupas are the most remarkable feature of the town of Patan that are testimony to an ancient architectural tradition. Marking the four corners of Patan, three of these stupas are merely mounds of earth with prayer wheels around them while the fourth near Shankamul is a beautiful concrete stupa. At the time they were built, Buddhism flourished in the Kathmandu Valley.
The historians have agreed that these Stupas might have been erected in connection with the foundation of Patan towards the end of the 4th century AD. Because of its circular base and hemispherical dome it can be safely said that these Stupas have not been constructed in accordance with the Buddhist architecture. It is said that Emperor Ashoka ever visited Kathmandu valley, there are four stupas supposedly built by him.
Lagan Thura- Southern Stupa
Among the four Stupas of Patan, the southern mound is known as Lagan Khel Stupa or Lagan Thura Stupa. It is the largest among the four, measuring 47.40 meters in diameter and 11.80 meters in height. The mound is crowned by a recent structure, a miniature cenotaph added on the top. The shrines of Tathagatas were presumable added in 1878; even as others were added to the eastern mound in 1846.An inscription tells us that on the western Stupa the Tathagatas were already in place by 1455.
Teta Thura – Eastern Stupa
This Stupa is located about 200 meters east of the Tyagal Tole of Patan near the Eastern ring road. This Stupa is comparatively bigger than the other two Stupas in the perimeter. The perimeter of this Stupa is 75.83 meters and height 10.4 meters. It has fire Vedica of height 1.6 meters with one Tathagata in each direction. The dome of 4.5m in height is paved with firebricks. A square-shaped Harmika enshrines the dome. No pre-18th-century inscription can be found on the structure. There are three stone inscriptions led in the Vedika. Two inscriptions are completely damaged and not legible and the one inscription left by the Tathagata Ratnasambhava is hardly readable.
Pucho Thura – Western Stupa
This Stupa is located just at the roadside of Pul Chowk Bus stand on the west end of Patan. The perimeter of this Stupa is 75.52 meters and height 12 meters. It has firebrick Vedika of height 1.2 meters with one Tathagata in each direction. The dome that is 6.5 meters tall is too paved by firebrick. It has no Harmika. The thirteen rings Cakravalis are constructed directly over the dome in a square-shaped pyramid structure. A Yasti is placed is on the top of the spire with a parasol.
Ibahi Thura- Northern Stupa
This Stupa is comparatively more complex and smaller than the other three Stupas. This is similar to the structure of Svayambhu Mahacaitya in Kathmandu. It is nearly circular and has a perimeter of 60.62 meters. It has five Buddha in the Vedika with their consorts except the Tathagata Vairocana. It has a Vedika of 1.5 meters and a dome of 5.5 meters in height. A square Harmika is constructed over the dome with 13 steps Cakravali and a parasol.