Helm's Dike
From Tolkien Gateway
Helm's Dike was the trench and rampart that blocked Helm's Deep. Behind it lay the fortress of Aglarond or the Hornburg, at the entrance to the Glittering Caves.
Helm's Dike was the trench and rampart that blocked Helm's Deep. Behind it lay the fortress of Aglarond or the Hornburg, at the entrance to the Glittering Caves.