Location from One Piece by Eiichiro Oda
The entry point to the Grand Line — a mountain at the intersection of the Red Line and the Grand Line where ocean currents flow UPWARD, carrying ships over the peak and down into the Grand Line on the other side.
Reverse Mountain is the threshold between the ordinary world and the extraordinary one. The bizarre upward-flowing currents — caused by the Grand Line's anomalous weather and magnetic systems — make this the only viable entry point for ships from the four Blues. It's exhilarating and terrifying: ships accelerate to incredible speeds on the ascent, with zero room for error in the narrow canal. At the summit, crews get their first glimpse of the Grand Line — and at the bottom, they meet Laboon. The giant whale has been ramming his head against the Red Line for fifty years, waiting for the Rumbar Pirates who promised to return from the Grand Line. They never did — all but Brook died to disease and pirates. Luffy drew his jolly roger on Laboon's scarred forehead and promised to come back, giving the whale a new reason to wait.
A massive mountain at the junction of the Red Line, with four upward-flowing canals carved into its faces — one from each of the four seas. Ships ride the currents at terrifying speed up the mountain's slope, cresting the peak before plunging down a fifth canal into the Grand Line. The walls of the canals are sheer rock; any miscalculation sends a ship crashing into the mountainside. At the base of the Grand Line side, the Twin Capes mark the entrance, where the lighthouse keeper Crocus tends to Laboon, a whale who has waited fifty years for his pirate friends to return.
Also known as: Reverse Mountain, The Gateway, Twin Capes