Castleton is a neat little place, in the Midlands of England. There was a huge castle on the top of literal mountain. It sit over a cave that has a river running through the cave. The name of the river is River Styx. Prisoners were dropped down a hole from the prison into the river. During flood stage, the river would carry huge boulders, which would circle around in this chamber below the castle. The first mix master grinder! This eliminated the problem of disposing of the remains of the prisoners. The dome of the chamber carved by those boulders was at least 30 feet over our heads. Fortunately, the river has been tamed, so no boulders now.
Keith and Caryl next to the River Styx in Castleton.