Soul King Palace

is the residence of the Spirit King, located in a separate dimension in the very core of Soul Society.

Overview
The route to the inner dimension in which the palace resides can only be opened with a golden, tri-pronged key fittingly named the, the location of which is kept secret, only being passed down verbally from one Gotei 13 Captain-Commander to the next.

The sekkiseki walls that surround Seireitei are ordinarily intended to protect the Reiōkyū, instead only falling down to Seireitei in times of emergency.

Royal Guard
The Royal Guard, also known as the "Zero Division", are the protectors of the Reiōkyū and its residents, particularly the Spirit King. Though they commonly remain within the palace, when the Royal Guard do need to travel, their preferred method of transportation takes the form of a huge pillar called the. While this pillar is able to freely exit the inner dimension, it is unable to return to the palace on its own and is instead entirely reliant on outside assistance to do so, such as Kūkaku Shiba's.