Great walls are massive fortifications erected to protect a population from an outside threat. Fictional great walls may guard a kingdom, country, or post-apocalyptic haven from raiders, monsters, or the undead hordes. They may protect countries, cities, or act as barriers between inhabited lands and the wilds or the wastes. They may be located on frontiers or on borders. There may be secret tunnels through the walls, or sapping tunnels underneath. Great walls may be made of stone, ice, bone, or other material.
Designing Fictional Great Walls
They may protect countries, cities, or act as barriers between inhabited lands and the wilds or the wastes. They may be located on frontiers or on borders between adjacent kingdoms. A common narrative theme with great walls is the discovery of which side of the wall is the correct one to be on.
While the size of great walls may be a deterrent to outside forces, it may not be the only one. Great walls may contain watchtowers, castles, gatehouses, great gates, and other elements along their length to support its defense and maintain its integrity.
Construction and Maintenance
Megastructures such as great walls are usually built over long periods of time (unless magic, gods, or other forces allow for faster construction). Portions of a wall may be older than others. Palisade walls and scaffolding may be present. Also consider what material the wall is constructed from. Stone, ice, and bone are all examples. This may also be an opportunity to include a fictional material.
Circumventing a Wall
Sneaking through great walls is a common narrative event while their destruction may be an important historical event. Fictional great walls may feature hidden doors, underground tunnels with secret routes between sides, or cave or sewer systems that offer passage beneath. If these sites are besieged (or are ruins that were at one point long ago destroyed) the walls may be damaged or completely collapsed in portions.