Romans in Britain
The Romans never quite succeeded in conquering all of Britain. They were partly successful, but the Celts, the people the Romans called barbarians, pushed back and blocked the Romans from total success.
The Roman Emperor Hadrian ordered a wall to be built in Britain to clearly mark where the Roman territory in Britain ended and the barbarian territory began. This wall was called "Hadrian's Wall". It wasn't really a wall across Britain. It was more like a small stone fence with guard posts along it. Parts of the wall still exist today.
The Roman invasion of Britain was not totally destructive. They did some good things too. They built roads, of course, strong forts, and new settlements. Mostly importantly, they also spread their language, culture, and laws.