Hillforts took masses of people to build them. But in some parts of the country, such as the northern Isles, there were not many people and clans were small, so any building project had to be on a small scale.
This is where you find the first stone towers. They may be the world's first castles, although we don't really know how they were used. Families also built homes called crannogs on stilts in lakes.
