The southern wall of Westfold was formed by the White Mountains, and in a part of that range was a broad vale, several miles across: the Westfold Vale. On the western side of this bight, a narrower valley led on into the Mountains. This was the Deeping-coomb, the entrance to Helm's Deep where the Rohirrim had taken shelter when the Dunlendings overran their land in III 2758. Centuries later, the armies of Saruman marched through the Vale and into the Deeping-coomb, only to be defeated at the Battle of the Hornburg.

Earlier editions of The Two Towers contain a slight but significant error regarding the Westfold Vale. Whereas Tolkien's original manuscript makes it clear that the Vale was itself a 'great bay in the mountains', the text was garbled in reproduction, so that the 'great bay' appeared to be a reference to the Deeping-coomb, rather than the entire Vale. This confusion has been corrected in later editions of the book.