Bhismaknagar is a hill fort made of burnt bricks situated in
, a small town in Lower Dibang Valley District
. The fort, built with clay bricks and embellished with pottery, has an elongated semi circular shape extending over an area of about 10 sq km. The Bhismaknagar Fort, which was first excavated in 1996-97, is proof of the penetration of the Aryan culture into Arunachal Pradesh
in the 4th century.