Bhismaknagar is an ancient archaeological site located in the Lower Dibang Valley of Arunachal Pradesh. It is one of the oldest historical sites in the region, believed to have been built between the 8th and 12th centuries. The site features the ruins of a fort made of burnt bricks and stone, reflecting the grandeur of ancient craftsmanship and architecture. Bhismaknagar holds cultural and historical significance, particularly to the Idu-Mishmi tribe, and is often associated with the legendary Bhishmaka, father of Rukmini from Hindu mythology. The place offers a glimpse into the rich heritage of Arunachal Pradesh and attracts history enthusiasts and spiritual seekers alike.