Rochester Castle began as a wooden fort built on the site of a Roman fort soon after the Norman Conquest. It was rebuilt in stone between 1087 and 1089 and the four story stone keep was added in 1127.
The south tower of the keep, originally square, was undermined and demolished when the castle was beseiged by King John in 1215. It was replaced with the round tower when the castle passed back into royal hands a short time later.
I have only reconstructed the keep of Rochester, the castle itself lies to the north. My reconstruction of Rochester Keep is 20 x 20 inches (64 x 64 studs) and is 22 inches high.
For more photos of my reconstruction of Rochester
For photos of the real Rochester Keep and other source