The Keep of Hedingham Castle is an excellent example of a Norman style stone keep. The building is nearly square, is four floors high, and once had a square tower at each corner. It was built in the first half of the 12th Century and is in Essex, England.
The entrance to the keep is on the second level and was reached by a staircase. The entrance building has been destroyed, but the foundations remain.
My reconstruction of Keep of Hedingham Castle is 20 x 20 inches (64 x 64 studs) and is 21 inches high.
For more photos of my reconstruction of the Hedingham Keep
For photos of the real Hedingham Keep and other source