I've found three little bits of copy regarding the larger world and the Nentir Vale's place in it:
- "A broad borderland region."
- "The Nentir Vale is a northern land..." and
- "(Harken Forest) separates the Nentir Vale from the more populous coastal towns of the south."
Sticking the Vale up along the northern border of the kingdom takes care of the first two points. Making the rest of this Nerath Empire remnant into a bastardization of southern England satisfies the third point as well a my current preoccupation with Bernard Cornwell's King Arthur books.
But please let me know if you've any better published sources for expanding the map, won't you? I'm working entirely from the DMG and H1.
Update: Misspelled "capital". D'oh!
Latest update: I got to thinking about Colmarr's comment that the Hammerfast trade route needed somewhere to go. It occurred to me if the Vale were on one side of a hellaciously vast mountain range, it would explain why people on the other side would refer to the mountains as something else beside "Dawnforge". Plus, a safe route through such rugged terrain really would be an asset worth guarding with a fortress. Thanks Colmarr! =)