The Marine Headquarters is the main division of the Marine organization that has jurisdiction over the Grand Line. Marine stationed here is considered "super-elites" among their peers. Ranks at other Marine bases are considered three-ranks below that of the Marine Headquarters.
The headquarters base of operation is currently at Marineford at paradise.
Base of Operations
The Marineford Headquarters is a large, fortress-like building that bore a sign containing the kanji for "Marines" and the Marines' symbol between them, and on top of this structure is a large, multi-story tower styled after an ancient Japanese pagoda. There are mountains at each corner of the structure that each have a small building on top carrying the Marine flag.
In front of the Headquarters is Marineford Town, where families of Marines stationed at Headquarters lived, and the Oris Plaza which contains an execution scaffold. The island itself is shaped like a crescent, and Marineford Bay is located in front of Oris Plaza.
The Marine Headquarters has an unknown number of branch bases scattered across the Grand Line.
G-1 is currently located in the New World.
G-2 is located near the Lilusia Kingdom
G-3 is located somewhere on the Grand Line.
G-4 is located somewhere on the Grand Line.
G-5 is located on the New World, near the Red Line. It's noted for its rowdiness, lack of discipline, and cruelty among the Marines stationed there.
G-6 is located somewhere on the Grand Line.
G-7 is located somewhere on the Grand Line.
G-8 is located in Paradise, below the sky island Skypiea. It is located in a rock formation in the middle of a cape and is heavily fortified, although rarely encounters trouble.
G-F is located on Fron Island in the New World, close to Totto Land. The base and its surrounding buildings are protected by forested cliffs encircling the island.