Places in Middle-earth
The Fortress of Aglarond
Súthburg (before King Helm's day)
Location: Built on the Hornrock, an outcropping of Thrihyrne which is the northern edge of a spur of the White Mountains (Ered Nimrais). The Hornrock projects from the northern side of the Deeping Coomb, and is connected to the southern wall of the Coomb by the Deeping Wall.
Description: At Helm's Gate, before the mouth of the Deep, there was a heel of rock thrust outward by the northern cliff. There upon its spur stood high walls of ancient stone, and within them was a lofty tower. Men said that in the far-off days of the glory of Gondor the sea-kings had built here this fastness with the hands of giants. The Hornburg it was called, for a trumpet sounded upon the tower echoed in the Deep behind, as if armies long-forgotten were issuing to war from caves beneath the hills.
TTT, Book III, Ch 7, Helm's Deep
The Gap [of Rohan] was watched by the fortresses of Aglarond (the Hornburg) and Angrenost (Isengard), and the Fords of Isen, the only easy entrance to Gondor [later Rohan], were ever guarded against any incursion from the "Wild Lands" [later Dunland].
Unfinished Tales, Part 3, Ch 5, The Battles of the Fords of Isen: Appendix
Contributors: Lyllyn 8.1.03; added Names & quote: Elena Tiriel 8.15.04