Fourtrees is the place in the center of all four clans in the old forest. It is where they had gatherings every full moon. There were four oaks at fourtrees, (hence the name) one stood for each clan. There was a giant rock called the Greatrock in the center where the leaders would stand to adress the clans at the gatherings. Bluestar and Oakheart met in secret here. When a leader gets their nine lives from StarClan, though they are at the moonstone they see themselves at Fourtrees. When the forest was being destroyed they twolegs took down the trees and the Greatrock, preventing the clans from having that full moons gathering.