Motte and Bailey Castles
They are called motte and bailey castles. The motte is the hill and the buildings on the top. The bailey is the protected area at the foot of the motte.
For 200 years motte and bailey castles were ubiquitous. There were hundreds scattered across England. All motte and bailey castles have since disappeared. We have only drawings, paintings and wall hangings to show us what they looked like -- and archeaological digs.
The lord of the manor and his entourage lived at the top of the hill protected from warring parties that might attack. The people who farmed the land lived below.
If you do an imaginative squint the hill we are approaching might have been the under structure for something like this.