The word castle has become a generic term used to describe many types of fortification around the world.
In the 13th century BC, the Hittites built stone walls with square towers around their capital in Turkey. The Egyptians built a fortress out of mud bricks, with massive gatehouses and square towers, to defend their southern borders, 1500 years BC. From the 16th to the 12th centuries BC, small, separate kingdoms dominated much of mainland Greece, each with its own fortified citadel.
The first fortifications began to appear in Britain from the 5th century BC, with the construction of Iron Age hill-forts. Maiden Castle in Dorset is one of the most impressive examples. These great earthworks (a series of ditches and raised earth banks) were topped by a wooden wall (palisade), and usually protected a settlement. However, they proved no match for the Romans when they invaded England in the 1st century AD. They quickly overpowered the hillforts and imposed their own authority on the land by constructing forts, built to a standard rectangular plan, across much of the country. Some were built quickly out of wood while others were more permanent structures built of brick or stone.
Roman walls at Portchester Castle
The remains of Roman forts can be found across the country, but the most impressive walls still standing can be seen at Portchester Castle in Hampshire, Pevensey Castle in East Sussex, Richborough Roman Fort in Kent, and Burgh Castle in Norfolk.