So people could visit them.
To look nice.
To give protection to the important people who lived in them and show everyone how rich they were.
To make poor people jealous.
To give the people who lived in them a nice view from the window.
It was easier to build them on hills.
To make it harder for people to attack the Castle.
So that the people who lived in them could go for a swim in the water.
At the bottom of the Catle walls.
At the Gateway.
On the Drawbridge.
At the top of the Castle walls.
They cost too much money to build.
They take too long to build.
When gunpowder was invented it was too easy to blow up the Castles and so they became useless.
People did not get paid enough money to build the Castles and could not be bothered to build any more.