Helm's Deep is a large valley in the North-western Ered Nimrais (White Mountains. The valley was fortified by a natural set of hills called Helm's Dike. From the hills lay the first stones of a fortress known as Aglarond or the Hornburg. The Hornburg is a fortress of Rohan, and the largest of all of them, and was situated above a massive cave system that led into the mountains. A tower was fixated above the fortress, the top was a massive horn, the horn of Helm Hammerhand, a former king of Rohan and the namesake of Helm's Deep.
The Battle of Helm's DeepEdit
In the Third Age, during the War of the Ring, Saruman the White sent a massive force of Uruk-hai to crush the Rohirrim while they were cornered within the Hornburg's stone walls. 10,000 Uruk-hai marched to the valley on March 3, 3019. Saruman himself had created a device that would blow up the culvert of the Deeping Wall, the only weakness in the fortress's otherwise impenetrable walls. The Uruks flooded into the Keep,killing all in their path. The Rohirrim retreated into the caves, while Legolas and Aragorn fended off massives swarths of Orcs on the stairway from the fortress to the Deep. A calvary charge from the Deep, led by Aragorn and King Theoden, rode out, driving the forces of Isengard out of the gates and into the Deeping-Coomb. Just as they were, Gandalf the White and Erkenbrand appeared with a thousand swordsmen on the Dike, who then charged down from the hill into the army of orcs; Saruman's army was cornered. The Uruks were massacred, and the Battle of Helm's Deep was won, at the cost of many for Rohan.
After the WarEdit
The demolished culvert was rebuilt by Rohan with the help of the Dwarves. Gimli and Legolas made a pact of friendship, that when the wars of their age ended, that Gimli should walk in the deep woods of Fangorn Forest and that Legolas should behold the jeweled-splendour of the Glittering Caves.