Avalon

The legendary capital megalopolis of the elves.
The rulers of Avalon are High King Felsien and High Queen Nimue, and the High Kingdom is overruled by the Fairy Queen Lady of the Lake Morgan le Fay. 
The five Kingdoms of Avalon are: Avalon, Valenar, Azarel, Oth, and Illien. 
Excerpt description from the Tales of Salus and Gale 
Llewellyn convinced his elfin folk to allow the boy to stay, for he was a wizard of credence and high regard in Avalon. Gale was shown where the elves had mastered their civilization in the forest; where lanterns of magic were lit across great tree houses and bridgewalks that lent paths for the elves to travel from one end of the kingdom to another, without ever having to lend their feet to the ground. There were tremendous stairways that climbed the tallest trees of Perth, giving way to the Seven Citadels and the canopy by which they fit together a paradise city. 
He flew the boy across the land where the forest met the pale rock ranges at the Lake of Avalon, and here the elves had erected a great metropolis in the mountain pass, whereupon was laid the palaces of Silvalar, and great concourses wrapped up and around, and inward the mountainsides so their people could proceed through marketplaces under open air roofs of rock. The city was built both deep within and around the mountain, while high above overlooking Faywood and the lands beyond were the floating islands of rock, which were the Elf Havens of Avalon that were dwellings in the clouds. There inlaid upon the peak of Tor Goldor there rested the High Throne and Scepter of the Elf Lands: The Sanctum of the King and Queen who Gale laid eyes on when Llewellyn was called on to kneel and show the boy.   
Main features of Avalon: The Lake and the Isle Havens, the High Peaks, Seven Citadels, Silvalar, the Elf Havens, the Timeless Tree, and the Scepter of the Elf Lands.