The Roving Bridge.

Today's history lesson takes us to this, a former canal used for the transportation of limestone for the nearby lime kiln.
The observant student will note the width of the canal is no more than two metres. The tunnel's unusual shape allows a tub boat and a (thin?) horse to squeeze through.
Advanced canal blippers can learn more here: https://en.m.wikipedia.org/wiki/Rolle_Canal

Many thanks to Marlieske for hosting Derelict Sunday.