This is where the watchtower of Amon Hen was constructed for the scene where Frodo and Aragorn reunite after Frodo hides from Boromir, who tried to take the Ring from him. Then Aragorn tells Frodo to flee and face an army of Uruk-hai alone, like a king.

If you want a better view of this filming location, you can watch my video on YouTube about the filming locations of the first movie.