The Red Line is a massive ring-shaped landmass that circles the entire One Piece planet and acts as a wall, dividing the globe. Combined with the Grand Line, it divides the sea into four quadrants, namely East Blue, North Blue, West Blue and South Blue.
The Red Line is constructed of a reddish mineral. It is claimed to stretch 10,000 meters underneath the sea's surface to Fish-Man Island on the ocean floor. At the same time, the Red Line's summit is sufficiently above sea level to be regarded as insurmountable. The Red Line is unbreakable as well. In addition, the Red Line, which spans the Grand Line, has its own "islands" for the seasons of summer, winter, spring, and fall, separating its weather conditions from the rest of the world.
Although it is unpassable, restricting passage to the Grand Line, there are some passageways and methods to cross the Red Line. Reverse Mountain is referred to as the entrance of the Grand Line among pirates wishing to enter it. Although it is not available for pirates, one could also hope to cross the Grand Line by gaining access through the World Government and passing through the Holy Land of Marijoa.
Even though it is impassable, there have been a few individuals who were able to climb it. Fisher Tiger managed to climb the Red Line barehanded to attack Marijioa to free the slaves from the grasp of Celestial Dragons. Additionally, Germa 66 also managed to climb the Red Line with their amphibious ships to travel from North Blue to East Blue.
Mary Geoise, the World Government's capital city, is situated atop the Red Line at the point where the Grand Line and Red Line converge. It is stated that it is located at the center of the world.
The Red Port includes specialized elevators called Bondolas, that reach Mary Geoise and permit individuals who were given access to cross the Red Line to travel through Mary Geoise. It is located at either end of the Grand Line, at the base of the Red Line, and immediately beneath Mary Geoise.
Reverse Mountain, where water from the four Blues flows up the mountain and down into the first part of the Grand Line, is located on the exact opposite side of the planet from Mary Geoise.
A. The New World is the name given to the second half of the Grand Line. It is located between West and North Blue, as well as Fish-Man Island and the other side of Reverse Mountain.
A. The Grand Line is an ocean current that roughly circles the entire planet's equator. The Calm Belt separates it from the Blues on both the north and south ends.