Zeus' Fist

Zeus' Fist is a pile of rocks in the forest of Camp Half-Blood. If looked from a certain angle it looks like a large fist. If looked from any other angle, it looks like a pile of deer droppings, but the campers are prohibited from calling it "Poop Pile," as Zeus tends to be picky about things that bear his name and Chiron believes it disrespectful to call something a "pile of deer poop" after it was initially named after the king of the gods. It was often used in Capture the Flag as a location for a flag, as it is clearly visible and hard to climb (now the campers stay away from it because of Kampe's death during the The Battle of the Labyrinth). The Fist also used to be one of the entrances to the Labyrinth.

The Titan's Curse
Percy and Thalia uses it as a place for the flag in the Campers-Hunters capture the flag game. Even though it is hard to climb, Zoë finds a way and gets up there very fast.

The Battle of the Labyrinth
During a training exercise, Percy and Annabeth found out that Zeus' Fist also serves as an entrance into the Labyrinth. Luke used the entrance in the Battle of the Labyrinth to get his army into Camp Half Blood. After the battle and Daedalus' death, all entrances to the Labyrinth, including this one, were destroyed.