Helm's Deep is properly the narrow gorge or ravine at the head of a larger valley (the Deeping-coomb), but the name is also used for the fortifications at the mouth of the gorge and the larger valley below. The gorge, which wound deep into the White Mountains at the feet of the Thrihyrne mountain, led into the Glittering Caves of Aglarond, an extensive series of spectacular speleothems. In "The Lord of the Rings", the Dwarf Gimli, who like all dwarves is well versed in geology, horrified that the caves are used only as a refuge, describes them lyrically: