Reverse Mountain

Reverse Mountain (リヴァース・マウンテン, Rivāsu Maunten) is a mountain at one of the points where the four Blues meet and is one of the two known entrances to the Grand Line. This place is unique in that rivers from the Blues flow up the mountain, meet at the top, and then flow down into the Grand Line. This is due to the fact that the mountain, being a "Winter Island" using Grand Line terminology, is much colder than the surrounding sea in the Blues but not in the Grand Line. Many pirates entering the Grand Line die before they can even go up the mountain, because the hostile water currents and storms force them to crash into the mountain walls. On the rivers' borders are several gates built by an unknown hand. The Laboon arc takes place here.

It should be noted that although Reverse Mountain is touted as the main way most ships enter the Grand Line (barring crossing the Calm Belts), the width of the passage between the cliffs is barely wider than Going Merry. Thus, larger ships should not be able to enter past the cliffs (including Don Krieg's flagship which is supposed to have entered the Grand Line). This may be a simple overlooked detail on the part of Oda.

First Appearance: Chapter 101; Episode 61