The Sennin World
Kingo is a flying island that is a part of the Sennin World and home to many Youkai and some Doushi; especially the Juutenkun. It was set up a very long time ago by one of the Three Great Sennin, Tsuuten Kyoushu.
Tsuuten Kyoushu is the leader of Kingo Island. Originally below him were the Three Strongest, So Dakki, Bunchuu, and Chou Komei, however they eventually broke apart. Beneath Tsuuten Kyoushu and the Three Strongest are the Juutenkun.
Kingo itself is estimated to be about five times that of Kun Lun Mountain. The radius of Kingo's base is around 15kms long.
Inside of Kingo
Kingo Island is far more complex in structure than Kun Lun. As it is home to about a thousand Youkai Sennin, each with different needs and specialties, Kingo has basically created special "realms" or "realities" within its own confines. Those sphere like structures are powerful, spatial paopei that are called "Akukans", which are used by the ten Juutenkun members as their homes and their weapon of choice.
The main Kingo Island is also surrounded by a multitude of smaller islands that are home to some of the more famous groups of Sendou around. For example, Kuryuu Island - one of the Kingo Island chains, is home of the Shisei.