Rohan is the name of the vast grasslands and plains that are home to the Rohirrim. The Rohirrim call themselves the Eotheod (Old English for "horse people") and their land the Riddermark - mark coming from the Old English mearc, meaning "a land within a boundary." Rohan is bounded by the White Mountains on the lower west and along the south, the Misty Mountains on the upper west, Fangorn Forest and the Limlight River to the north, and the Anduin River to the east. Rohan is divided into five districts:

- Wold ("Open Hills"): The hilly area below the Limlight River is due east of Fangorn Forest on the west side of the River Anduin. (This reference probably comes from the Weald, a region of domed hills in southwestern England.) The wold stretches to the east side of the Anduin, where it is known as the Brown Lands, formerly the great garden of the Entwives.

- Eastemnet ("East Plain"): This plain lies east of the Entwash River.

- Westemnet ("West Plain"): This one lies west of the Entwash.

- Westfold ("West Earth"): This valley or basin at the western foot of the White Mountains contains the fortress of Helm's Deep.

- Eastfold ("East Earth"): This valley at the eastern foot of the White Mountains holds the royal city of Edoras.

There is a break between the end of the Misty Mountains (where Isengard stands) and the beginning of the White Mountains. The Isen River flows through this break, known as the Gap of Rohan. The Gap connects Rohan with the western lands of Arnor called Dunland, where the wild men known as Dunlendings live.

Source: The Origins of Tolkien's Middle-earth for Dummies by Greg Harvey
Copyright: 2003 by Wiley Publishing, Inc., Indianapolis, Indiana