The Crossing, also known as The Twins, is castle that starts off belonging to the North faction. It is located South of Moat Cailin. The castle acts as a land bridge across the Green Fork, which is the northernmost river of The Trident. The player or any NPC's can cross the river at The Crossing, no matter what their relationship is with the faction currently in possession of the castle.
At The Crossing you can recruit Crossing Man-at-Arms.