Twin Cape is located at the bottom of Reverse Mountain, at the exit that leads into the Grand Line. The area is located precisely where the Red Line and the Grand Line meet. From here, sailors can choose one of the seven routes of the Grand Line by waiting for the Log Pose to set on the desired one.
The lighthouses are located at the exit of Reverse Mountain, and are where the Reverse Mountain Arc took place. Crocus has been the caretaker of the northern lighthouse for at least 52 years, taking care of Laboon as well, minus the three years he spent as the doctor of the Roger Pirates.