Geological / environmental event
An Elf named Veris, who was the greatest Sorcerer the world has ever known, in a display of power the likes of which had never even been heard of before, rips Orchestria, a half-mile wide city, and lifts it a mile above the ground. There it permanently floats, and is the permanent residence of the Elves there, who will come to be known as High Elves. Veris is named First Conductor of the High Elves of Orchestria. Humans are forced to rebuild their homes in and around the crater below.