A medieval castle had two purposes: it was both a fortification and the home of a lord.
The first castles were just earthwork enclosures.
Later, earth mounds and timber towers were built, forming a type of castle called a motte and bailey.
However, the timber constructions were vulnerable to fire, so shell keeps were built to protect the wooden structure within a stone wall — or shell.
During the time when the motte and baileys were being built, powerful noblemen were constructing the Norman great towers.
There was no tactical reason for building them so high.
The great tower — in all its forms — became a symbol of power and nobility.
The curtain wall was the castle's most important defensive feature.
At first, it was just a wall with a crenellated parapet but, over time, the defences developed.
Wall towers were added.
