Marineford

Marineford is the main headquarters of the Marines. It is where Fleet Admiral Sengoku and the three Admirals reside, along with many Vice Admirals and lower officers when they aren't assigned to another base. The Marine HQ is one of the three great powers, alongside the Shichibukai and the Yonkou. .Oda has stated that the grand line marines or rather the HQ marines would be about 3 Ranks higher if they were in any of the Blues.

It is situated near the Sabaody Archipelago, and lies directly next to Mariejois on the Red Line. The only safe way to reach here is through the Gates of Justice.

History
Shortly after the defeat of East Blue's most powerful pirates in the hands of Monkey D. Luffy, the higher officers here granted him his first bounty of 30,000,000.

Whitebeard Pirates' second division commander Portgas D. Ace's public execution is scheduled to take place here in, as of Chapter 539, less than four hours. To prevent Whitebeard and his crew's attempt to save their comrade, all of the Marines, along with the Shichibukai, has been summoned here to prepare for war. This may be one of the world's most shaking events. Jinbei, however, caused an outbreak in the headquarters in his refusal to cooperate, and was transferred to Impel Down.

As of recent chapters, Marineford has been declared target by Monkey D. Luffy in his attempt to rescue his brother, Portags D. Ace from his impending execution, and is currently causing a mass riot within Impel Down as he musters enough man power for an imminent assault upon Marine Headquarters