Aeolia is the colossal free-floating island that serves as the wind god Aeolus' headquarters and as a fortress in times of war.
It is made of glowing purple stone, and as wide as a football stadium with rugged cliffs on the side that were riddled with caves and holes. The island drifts around America, but usually stays close to mountain tops and is often found above Pikes Peak. It's connected to land via a thin ice bridge.
The island is comprised of four large gardens, representing the four seasons and the four Anemoi. To the right from the bridge is a snowy field with bare trees, a frozen lake and snowmen that appear to be alive, it represents Boreas and Winter. To the left from the bridge is a yard of Autumn leaves and trees, the winds makes the leaves into people very briefly, this represents Eurus and Fall. Past the Winter field is a grass terrain with sheep made of clouds, it represents Zephyros and Spring. Past the Autumn field is a desert with tumbleweeds that makes pictures and words in the sand, this represents Notus and Summer.
In the center of the four gardens is a castle with brass walls in the center. It's inhabited by Aeolus and his various assistants: wind nymphs, aurae, harpies, and other creatures of the wind god's domain as well as many paper airplanes. It also serves as the prison for captured storm spirits. Through the ice bridge, Aeolous can control who enters in Aeolia. If the wind god doesn't want you there and you're not Ouranos, it's very unlikely that you'll enter.
Jason and Odysseus, both mission commanders, have been there twice. They are the few known mortals that have visited the island. Both of them went there to get information about their missions since Aeolus, together with Helios supposedly knows almost everything.
Jason Grace, Piper McLean, Leo Valdez, and Coach Hedge visit the island to talk to Aeolus. When Leo is crossing the bridge with Thalia and Jason, he finally realizes that Jason might be a union to make two camps reunite in order to fight a bigger enemy.