Mary Geoise

The Holy Land of Mariejois (聖地マリージョア, Seichi Marījoa) is the capitol of the World Government and serves as another gateway to the Grand Line. The Government's HQ is there and the Council of Kings meets there.

History
It's not known how long Mariejois has been around. The earliest known history that Mariejois was around in 1127 when the King of Lyneel has to request permission from Mariejois to enter the Grand Line.

It may be 800 years old after the Void Century.

In 1510, it was here that Spandam manipulated the Gorousei.

In 1516, the Council of Kings took place in Mariejois.

Current Storyline
During the Jaya arc, two of the Shichibukai met here along with Mihawk. Sengoku also resides in Mariejois. It is here that the Gorousei reside also.

In chapter 303, we briefly see the Gorousei talking about Aokiji.

In chapter 433, we see Mariejois again as the Gorousei hear the news relating to Shanks and Whitebeard.

Location
It's unknown where Mariejois is located, some say it's on the Red Line but as of now it's not confirmed yet.

World Government HQ:

This is where Sengoku resided along with the Gorousei. This is where the Shichibukai meet, and this is also where we see Lafitte for the first time.