Castle Black is a stronghold located at the northern end of the Wall, a massive ice structure that separates the Seven Kingdoms from the dangers beyond. It serves as the primary base for the Night's Watch, a sworn brotherhood tasked with defending the realm from threats such as wildlings and mythical creatures. The castle is built from black stone, giving it its name, and features a large gate that leads to the wilderness. Inside, it houses barracks, a training yard, and a commander's quarters. Castle Black plays a crucial role in the defense of the realm and the stories of A Song of Ice and Fire.