Bihar and Vasu-Bihar are two villages, situated about 4km to the west of Mahasthangarh. The Nagar river passes through the present Bihar village and, on its western bank, there is a very large brick mound, approximately measuring 213.3m × 182.8m. About 1.61km northwest of this place is the Vasu-Bihar village, where there is another considerably large mound, about 9.14m high, locally known as Narapatir Dhap. A little south or this ruined mound lies a large tank known as Jhinjhrailer Dighi. Close to it on the northwest, the ruins of a temple with carved and ornamental bricks is visible, which now bears the name of Sanyasir Bari. Beyond that on further south lies the Susong Dighi or Sasanka Dighi, traditionally known to have been excavated by king Sasanka (606-636 A.D.). Another large ancient brick mound also is visible towards the south of the Bihar village, situated on a large tank.

The famous Chinese pilgrim, Yuan Chwang, in his itinerary has mentioned Po-Shi-Po, the name of a grand monastery situated about 6km west of Pundravardhana (Pan-na-fa-tan-na), which he visited. Cunningham identifies this Po-Shi-Po either with the mound located at Bihar or at Vasu-Bihar. The pilgrim found here ‘a grand monastery remarkable for the size and height of its tower and pavilion. It was occupied by no less than 700 monks who studied the Mahayana; and men famous for their learning flocked here from the eastern districts. At a short distance from the monastery there was a stupa built by Asoka on the site where Buddha explained his laws to the Devas. Near this was a spot where the last Buddha had taken exercise and rested, traces of his foot-marks were still to be seen’.‘Not far from the last place there was a temple containing the statue of Avalokitesvara which manifested its divine powers by prodigies’.

Cunningham identifies the great monastery of Yuan Chwang with the extensive brick mound of the Bihar village itself. The lofty stupa built by Asoka, he thinks, is well represented by the solid brick mound at Vasu Bihar (present Narapatir Dhap), to the east of which is a large tank (present Jhinjhrailer Dighi).

He further identifies the Vihara containing statue of Avalokitesvara with the small ruined temple to the north-west of the Asokan Stupa (present Sanyasir Bari). He describes that ‘It is a small building, only 3.9m ×3.3m inside, but the walls are 1.21m thick and it is surrounded by a wall forming an enclosure 31.69m long from north to south by 19.50m broad. The entrance is on the south towards the stupa. No remains of sculpture could be found, but there were plenty of carved bricks, both in situ in the walls and scattered about the ground. Recent excavation, however, has revealed the derelict relic of a medium size Buddhist monastery at village Bihar and a group of three smaller monasteries at village Vasu-Bihar. They have been dated in the 7th- 10th century A.D.