Wall

The Wall is a colossal abandoned fortification which stretches for roughly 300 miles (500 kilometres) along the northern border of the Seven Kingdoms, separating the realm from the domain of the wildlings that live beyond. It is over 700 feet and is constructed out of solid ice. It was supposedly constructed using both magic and mundane means some eight millennia ago, in the aftermath of the Long Night, to protect the realm against the White Walkers, although as they faded into myth, defence against the wildlings became the Walls the primary purpose. The maintenance and manning of the Wall was the primary purpose of the Night's Watch, who fulfilled their role right up until the re-emergence of the White Walkers in the Great War.

The Night's Watch abandoned the Wall following its breaching by the Night King. In the Great War's aftermath, with the Night's Watch all but destroyed, the Wall rendered obsolete due to the large breach, and cordial relations established with the Wildlings, the Night's Watch was formally dissolved and the Wall was permanently abandoned, allowed to fall into disrepair, with no effort made to control crossings.