Caverns of Helm’s Deep

The wide valley that would be known in later history as Helm's Deep ran into the foothills of the northern White Mountains. At the head of the vale, caves ran into the hills behind, and these led into a complex of deep chambers that ran back far into the mountains. These caverns were filled with shapes formed from the rock, glistening in many colours: pillars and spears, as well as other forms, fluted or cloud-like in appearance. The cave walls glistened with gems and crystals and veins of ore. At least in later times, secret ways led through the caves and out onto the hills behind.

These many-hued forms gave the caverns their name: Aglarond in Elvish, translated as the 'Glittering Caves'. In the early days of Gondor, the valley was chosen as the site of a fortification, and the Gondorians built a high tower and a wall at the head of the vale to guard the Gap of Calenardhon that ran to the north. At this time, the defensive post was named Aglarond, after the caverns that ran behind.

When Gondor ceded its northern territory of Calenardhon to the Rohirrim in III 2510, the valley and its caves became part of the new kingdom of Rohan, and the hereditary guards that had held the keep were transferred to Isengard to the north. The Rohirrim gave the caverns a new name in their own tongue, Glǣmscrafu, which, like the old name Aglarond, meant 'Glittering Caves'.

The Rohirrim used the caverns as a refuge in times of dire need, and indeed they were likely² used as such during the Long Winter of III 2758, when Rohan was overrun and King Helm and his people were driven into hiding. The Rohirrim took shelter behind the Hornburg (as they named the castle that guarded the ravine), and the entire valley came to be known as Helm's Deep from this time.

The caverns were used as a refuge again during the War of the Ring, when the people of Westfold fled into the caves as the armies of Saruman marched on Helm's Deep. The wide chambers of the caverns were said to have contained three quarters of the entire people of Westfold at this time. It was during the ensuing Battle of the Hornburg that the Dwarf Gimli was driven back into the caves, and was transfixed by the shimmering beauty he found within, calling the caverns a wonder of the Northern World.

After the War of the Ring, Gimli brought a party of his people from Erebor, and settled in the Caverns of Helm's Deep. He thus became the Lord of the Glittering Caves, and over the time that followed, these Dwarves worked to illuminate and extend the network of caverns beneath the White Mountains. His people rendered great aid and service to the people of Rohan and of Gondor into the Fourth Age.

The Caverns of Helm's Deep are one of the few locations in Middle-earth for which we can trace Tolkien's direct inspiration. Of the poetic description of the caverns given by Gimli, Tolkien says '...the passage was based on the caves of Cheddar Gorge and was written just after I had visited there in 1940...' (The Letters of J.R.R. Tolkien No. 321, dated 1971). Cheddar Gorge is a feature in Somerset in southern England, noted for its extensive cave systems.