Underwater Forges of the Cyclopes

"He's a Cyclops.They work the forges of the gods. They have to be immune to fire. That’s what I was trying to tell you."

- Annabeth Chase

The Underwater Forges of the Cyclopes is a forge near an underwater volcano. This forge makes weapons for the forces of Olympus.

The Sea of Monsters
According to Annabeth, Cyclopes work in the underwater forges of the gods. These forges are located underwater in Atlantis (Poseidon's Kingdom). Not much is known about its setting except that it is under the sea and the workers have to work in volcanic conditions.

The Cyclopes had apparently always worked with Hephaestus. One of these forges, where Hephaestus creates metal monsters, is mentioned to be located in the Sea of Monsters.

The Titan's Curse
Percy sends an Iris Message to Tyson who is working in the forges to make weapons.

The Last Olympian
After Percy is blown off the Princess Andromeda, he sinks to the bottom of the ocean to Poseidon's Palace. There he hears Tyson talk about how Briares is teaching the cyclopes the old ways of making weapons. While Tyson does enjoy working in the forges to make weapons, he feels he would do better on the front lines helping his father fight Oceanus, who has been attacking Atlantis.

Later, the Titan army invade the forge and Tyson leads the other cyclope into battle against them. The end result of the battle is unknown as Poseidon appears later to aid in the defeat of Typhon, the the current state of the forge is unknown, but it has presumably been rebuilt.

Trivia

 * According to Grover, the food in the forges is terrible.
 * In The Titan's Curse, we see that it is possible to send Iris Messages in the forges, as Percy sends one to Tyson in the book.