The Holy Land Mariejois (聖地マリージョア, Seichi Marījoa?) is the capital of the World Government and functions as the primary path which individuals seeking to enter the other, far more tumultous and dangerous side of the Grand Line, New World, pass through. This route is open only to persons within the juristiction of the law or in other words, Marines and World Government agents. This elegant capital furthermore serves as the headquarters of the World Goverment, the main governing body of the One Piece world. Mariejois' significance and unrivaled importance is also illustrated by the fact that the Council of Kings meets here on a regular basis in order to discuss current international events and propose and implement solutions.

Not much is seen of Mariejois in any of its appearances. The only exception to this is the gigantic palace, where the Gorosei meet. This palace is seen to have at least six floors, plus extra structures on top, including a number of towers. Also, in all of its appearances, the palace has been shown shrouded in white mist. The (assumed) main entrance of the palace is guarded by a group of soldiers clad in armor, which is something not seen elsewhere to date in all of One Piece. There are three known locations in the palace; the room where the Gorosei meet, an unknown location consisting of a sort of outdoor area with a large pond, and the apparent office of Kong. The latter is shown in much detail: A huge room encircled by an aquarium that contains what appear to be Sea Kings, with a slightly spherical chair at a large desk for Kong, as well as a chair and couch for guests.

The people who are allowed to live here are the World Nobles, one of them being Saint Roswald.