The ruins of a ruin

The Fonthill estate had the usual compliment of architectural exuberances. The particular one i was looking for here was a sort of grotto tunnel thing passing under the road and leading up to the remains of Fonthill Abbey. I'd stumbled upon it purely by accident some years ago while out with KK, looking for the remains of the Abbey. Now, on my own and armed with a fancy camera, i was hoping to find it again and get a few decent snaps. Looking at the OS map i could see 'Grotto' marked at a particular spot and headed out there to explore.