A city of the Dúnedain situated in the southern portion of the North Downs, north of Bree, at the northern end of the Greenway (North-south Road).

In TA861, when Arnor was split into three Kingdoms, Fornost was declared the captal of Arthedain. In TA1349, after the line of Isildur had died out in both Rhudaur and Cardolan, the kings of Arthedain declared Fornost to be the capital of all Arnor, and from that year on took the prefix "Ar" in their names.

In TA1974 the Witch King took Fornost and moved his capital there. While the forces of the Witch King were defeated in the very next year and driven from Arnor, Fornost was never repopulated.

In later years the majesty of Fornost was forgotten and the ruins of the city became known as Deadmens Dike.