In the works of J. R. R. Tolkien, Weathertop (Sindarin Amon Sûl, "Hill of Wind") is a hill in the Eriador region of Middle-earth, the southernmost and highest summit of the Weather Hills. The hill itself is of great importance in the history of Middle-earth, as chronicled in The Lord of the Rings, since it was a major fortress of the kingdom of Arthedain, home to one of the seven palantíri, and the site of several battles.
Weathertop overlooks the Great East Road east of Bree, about midway between the Shire and Rivendell. The hill rises a thousand feet above the level lands round about, and was the site of a watchtower in the days of Arnor. The watchtower and fortifications were burned and destroyed in T.A. 1409, but the top is still flat and surrounded by a ring of stones. A path leads from the top northward, connecting to the other fortresses of the Weather Hills. The tower originally held one of the seven palantíri.
Weathertop is mentioned in The Hobbit after the dwarfs escape the wargs and orcs, but is a scene of action in The Lord of the Rings. After fleeing from Bree, Strider and the hobbits avoid the main road and approach Weathertop from the north. At the top they discover a cairn with a message from Gandalf, and see the Ringwraiths approaching in the distance along the road. That night, the Ringwraiths attack their camp in a dell below the summit, stabbing Frodo with a Morgul-blade, but are then driven off by Aragorn.
Tower of Amon Sûl 
The Tower of Amon Sûl is a watch-tower on Weathertop hill. It was once tall and fair, but by the end of the Third Age only ruins remained. The Tower of Amon Sûl was built by Elendil in the first days of the North-kingdom of Arnor, which was founded in 3320 of the Second Age. At that time, the seven palantíri were divided and placed in different parts of Gondor and Arnor. The largest and most powerful palantír in the North was kept in the Tower of Amon Sûl. The Stone of Amon Sûl was the chief palantír used for communicating with Gondor. The palantír was kept on a round table of black marble with a curved depression in the surface where the seeing-stone was set.
When Arnor was divided into three kingdoms in 861 of the Third Age, the Tower of Amon Sûl was claimed by Arthedain and commanded the east road into Rhudaur from Cardolan. Also a special warden was posted there to guard and maintain the palantír. But Cardolan and Rhudaur also wanted possession of the Tower and its seeing-stone and there was strife among the three kingdoms.
In 1356, King Argeleb I of Arthedain was slain defending the Weather Hills against an assault from Rhudaur, which was then ruled by an evil lord of the Hillmen who had secretly joined forces with the Witch-king of Angmar. Arveleg, son of Argeleb, drove back the invaders and defended the Weather Hills for many years. But in 1409, Weathertop was surrounded by a great host from Angmar. Arveleg was killed and the Tower of Amon Sûl was burned and razed. The stone (palantír) of Amon Sûl was rescued by the forces of Arthedain, but it was later lost at sea.
Over time the ring of stones that had once been the foundation of the Tower of Amon Sûl crumbled and became overgrown with grass. When Gandalf came to Weathertop on October 3, 3018, he was besieged by the Nine Ringwraiths in the ruins. There was a great battle on the hilltop, and when he escaped Gandalf left a cairn of broken and burned stones in the centre of the ruins. Gandalf marked the topmost stone with the G rune and three strokes to indicate that he had been there on October 3. Aragorn interpreted the message when he came with the Hobbits to Weathertop on October 6. Later that night in a dell on the western side of Weathertop, five Ringwraiths attacked and Frodo Baggins was gravely wounded by the Witch-king before the Ringwraiths withdrew and Aragorn led the Hobbits away.
Weathertop and the Tower of Amon Sûl (named or unnamed) appear in film adaptations of The Lord of the Rings such as Ralph Bakshi's 1978 animated film and Peter Jackson's 2001-2003 The Lord of the Rings film trilogy. Unlike the original where it was no more than a ring of stones, in Jackson's film it is portrayed as having at least one-storey walls with stairs left inside the building and with almost complete monuments surrounding what was originally some kind of a hall. This was filmed in a studio set. The approach to Weathertop by Aragorn and the Hobbits in The Fellowship of the Ring (film) was filmed on a farm in the Port Waikato area of New Zealand.
Weathertop also features in The Hobbit: An Unexpected Journey when a band of Orcs led by Azog camp on the summit of Weathertop when searching for the Party of Dwarves to seek revenge after the Battle of the Gates of Moria
The tower of Amon Sûl is also present in several video game adaptations, such as: The Fellowship of the Ring, Conquest, Lord of the Rings Online and The Battle for Middle-earth II (a bonus map, available only in Collector's Edition).
- Tolkien, J. R. R. (1954), The Fellowship of the Ring, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), "A Knife in the Dark", "The Council of Elrond", ISBN 0-395-08254-4
- Tolkien, J. R. R. (1954), The Two Towers, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), "The Palantír", ISBN 0-395-08254-4
- Tolkien, J. R. R. (1955), The Return of the King, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), Appendix A, "The North-kingdom and the Dúnedain", ISBN 0-395-08256-0
- Tolkien, J. R. R. (1980), in Christopher Tolkien, Unfinished Tales, Boston: Houghton Mifflin, "The Palantíri", ISBN 0-395-29917-9
- Hammond, Wayne G.; Scull, Christina (2005), The Lord of the Rings: A Reader's Companion, London: HarperCollins, Nomenclature of the Lord of the Rings, ISBN 0-00-720907-X
- Fonstad, Karen Wynn (1991), The Atlas of Middle-earth, Boston: Houghton Mifflin Harcourt, ISBN 0-618-12699-6, which has a detailed map of the hill
- Tyler, J. E. A. (2004). "'Amon Sul' or 'Weathertop'". The Complete Tolkien Companion. Thomas Dunne Books. ISBN 0-312-31545-7.