The Walls were built more than a century ago, when humanity started to become extinct at the hand of the Titans. In response to this looming threat, the humans made huge walls to protect their last stronghold. The walls reach about 50 metres in height and reach four or five times a human's height below the ground. They also seem to extend surrounding the human territory underground and were once mistaken for bedrock. The tops of the walls are lined with cannons, which can fire on approaching Titans.
The walls are too long to be guarded in their entirety. To account for this, each one has four towns on their periphery. As Titans are drawn towards large concentrations of people, humanity can focus its defenses at these towns.The interior of the walls seems to contain numerous dormant Titans. While no details have been given, it has been suggested that the walls were originally created by Titans using their hardening ability.
Few people know about the Titans within the walls. The Survey Corps learned of their existence when the Female Titan damaged the surface of Wall Sina, exposing the face of a huge titan. Pastor Nick, a foremost member of a cult which considers the walls to be holy, knew of the titans within the walls, but would reveal no more under the interrogation of Hange Zoe. It is unknown how commonplace this knowledge is within the Wall Cult.
|Wall Maria is the outermost wall of the human kingdom. Its radius is 480 km. Like the other walls, Wall Maria is approximately 50 meters in height. The distance between Wall Maria and Wall Rose is around 100 km. Five years ago, it was breached by the Colossal Titan after about 100 years of peace and prosperity.|
|Wall Rose is the second outermost wall following Wall Maria. It is 380 km in radius. The distance between Wall Rose and Wall Maria is 100 km, and the distance between Wall Rose and Wall Sina is 130 km. It has been breached by the Colossal Titan after 5 years of the Wall Maria being breached, but has been covered by a boulder with the help of Eren Yeager. It was thought to have been breached again after Titans appeared inside it.|
|Wall Sina is the innermost wall protecting the kingdom where the king and other civilians reside. It is 250 km in radius. The distance between Wall Sina and Wall Rose is around 130 km. The city inside Wall Sina is protected by the Military Police serving under the king.|