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. A wall, too, the men of old had made from the Hornburg to the southern cliff, barring the entrance to the gorge. Beneath it by a wide culvert the Deeping-stream passed out. About the feet of the Hornrock it wound, and flowed then in a gully through the midst of a wide green gore, sloping gently down from Helm’s Gate to Helm’s Dike. Thence it fell into the Deeping-coomb and out into the Westfold Vale.