The Flying City of Anemos, the city of Wind.

To be truthful, it isn't the entire city that flies far above the ground. In the very center of the city which still rests on the ground, there is a huge crater in the middle, which is where the flying city once sat. The abandoned ruins of the grounded city reveal why, as many monsters and bandits call this part their home, attacking any that draw too close. It was due to this that the citizens decided to put all their power together to make a part of the city which would fly and rest in the air. Only those with the ability of flight or teleportation seem to be able to reach the flying city, though.