The Grand Line is the ocean current that follows an imaginary line that runs from north-west to south-east across the middle of the world and perpendicular to the Red Line. It is commonly reffered to those in the 4 Blue Seas as "the Pirate Graveyard." The Red Line is a vast continent that circles the globe from north-east to south-west. These two lines divide the two oceans of the world into four seas or Blues: North Blue, East Blue, West Blue, and South Blue. This stretch of ocean is said to be the most dangerous place in the world, and is sometimes referred to as the Pirates' Graveyard because of this reputation. Most believe that it is impossible to safely leave the Grand Line save at its beginning and end; however, the World Government regularly sends ships across the Calm Belts by coating their hulls with Kairoseki - this renders them invisible to the Sea Kings. The Grand Line is similar to the equator.