Shalban Rajar Badi and Kachari Chinese pilgrim hiuen-tsang noticed 20 Buddhist viharas and 100 Brahmanical temples while he visited pundranagara (Mahasthan, Bogra) during 637-645 AD. At present only three Buddhist viharas could be seen in the region which have been excavated by the Department of Archaeology. Unfortunately, the whereabouts of the rest of the viharas are not known. The mounds Shalban Rajar Bari and Kachari seem to have been visited by Hiuen-Tsang.
Shalban Rajar Badi The mound popularly known as Shalban Rajar Badi lies on the western part of village Arola under Paikar union of Kahaloo upazila in Bogra district. It is located 3.25km southeast of river Nagar and 7.25 km southwest of Mahasthan citadel on the western bank of a large tank covering an area of 30 hectares and known as Masan Dighi. The mound is square in shape and measures about 110m north to south and 108m east to west. It is about 9m high from the surrounding fields. There is a deep depression in the centre of the mound giving the appearance of a tank. The area of the mound is about one hectare. The shape of the mound represents a monastery type configuration. Bricks are abundant in the mound.
Several brick walls are seen in an exposed section. The bricks are 30 x 28 x 5 cm and 27 x 25 x 4 cm in size. Clay has been used as mortar in building the walls. Ancient ceramics are found all over the site. The shape of the mound appears to represent a Buddhist vihara.
Shalban Rajar Kachari The mound, popularly known as Shalban Rajar Kachari is situated on the eastern part of village Baghahali under Paikar union of Kahaloo upazila in Bogra district. It is located to the north of a large bil, locally called Makra, and is about 5.5km southwest of Mahasthan citadel. The imposing mound measures about 150m east to west and 300m north to south. Its height varies between 3 to 6m from the surrounding fields and it covers an area of about 4.5 hectares. Brick robbers have exposed three walls on the northwest corner. The width of a wall is 2.10m and height is 4m. The bricks are 33 x 29 x 5 cm and 27 x 25 x 4 cm in size. Clay has been used as mortar in building the walls. The shape of the mound appears to represent a Buddhist vihara.
About 7m east of the mound there is another mound locally called Chiringi Dhap which measures about 60x60x4m. Brick buttresses have been exposed on the northern side of the mound. The whole mound contains a large number of bricks. The bricks are 35 x 31 x 5 cm and 29 x 19 x 4 cm in size. Clay has been used as mortar in building the walls. Terracotta balls and figurines have been reported by local people. The mound seems to represent a stupa or temple outside a Buddhist vihara.