Moat Cailin is said to be the oldest fortress in Westeros, raised by the First Men over ten thousand years ago to protect the North from attack. It consisted of twenty towers overlooking the causeway leading out of the Neck, only three of which remain standing. Although long fallen into ruin, Moat Cailin is still extremely formidable, as it is nearly impregnable by an attack from the south. Great basalt stones as large as cottages once made up a curtain wall as high as that of Winterfell’s. It is said that a few hundred archers could hold Moat Cailin against an army many times its size for some time.
Moat Cailin’s Gatehouse Tower is still sound and boasts a few feet of standing wall to either side. The Drunkard’s Tower in the bog where the south and west walls had once met, leans heavily. The tall, slender Children’s Tower has lost half its crown. The wooden keep within the fortress rotted away a thousand years ago. All three towers are green with moss, and a tree is growing out from between the stones on the north side of the Gatehouse Tower.
Moat Cailin is surrounded by quicksands and suckholes and is teeming with snakes. An army would have to wade through waist-deep muck and a moat full of lizard-lions, and then scale walls slippery with moss while archers fired from the other towers. Saltspear is the long, narrow bay west of the Neck. It connects to the Fever River, whose headwaters are less than twenty miles from Moat Cailin. A dozen streams drain the wetwood of the Neck, all shallow, silty, and uncharted. They cannot be called rivers as the channels are always drifting and changing. There are ways through the Neck though that are not on any map, known only to the crannogmen, such as narrow trails between the bogs and wet roads through the reeds that only boats can follow. The Neck is riddled with endless sandbars, deadfalls, and tangles of rotting trees.
Moat Cailin was captured by an attack from the north led by Victarion Greyjoy during the War of the Five Kings. Although Victarion returned to the Iron Islands to partake in the Kingsmoot which saw his brother Euron Crow’s Eye become King, his men continue to hold Moat Cailin against the Bolton armies to the south seeking to return home.