The Nasunugan Ruins is a reconstruction of an old structure used by early settlers in the island as watchtower against Moro raids between 1765 – 1774. When the settlement was razed to the ground by the invaders, what was left of the structure were the blocks of stones and corals. These were used for reconstruction in 2000.

The ruins is located in Brgy. San Roque, about 5–10 mins from Biliran town proper, believed to be the site where Fr. Gaspar Ignacio de Guevarra built a fort as sanctuary of the early Biliranons.