This is a castle a guy built to use as a target for his trebuchet (catapult) 'Yankee Siege'. In the fall he does demonstrations tossing pumpkins at it.
I can't find the actual catapult around anywhere though.
Roadside Attractions, Castles
Links: www.yankeesiege.com
By: kjfitz
http://virtualglobetrotting.com/map/31689/