This is what a river leaves behind when it stops. About twelve thousand years ago, as the last ice sheet gave way, meltwater draining from Lake Algonquin toward Lake Iroquois cut the Kirkfield Spillway, and the Indian and Otonabee rivers ran through it. Not as they run now. The modern Indian River is shallow and slow; what came through here then was closer to the Niagara, deep and fast and carrying rock.
That water did two things to the limestone. It opened seven caves, and it drilled kettles: round shafts ground straight down into the bedrock by stones caught in a whirlpool and spun in one spot for long enough to bore a hole. Standing at the top of one is the clearest picture of the force involved that you will get on the surface.
The caves themselves are cavities in limestone rather than the decorated show caves further south, so there is not much in the way of formations. What there is instead is genuine squeezing and scrambling, in the dark, on your hands and knees. One of the seven sits at a permanent two degrees Celsius.
It is run by the Otonabee Region Conservation Authority as a conservation area near Warsaw, Ontario, with limestone cliffs and ledges, underground channels and the river on top of the whole system.
Caving here is unguided, which is unusual and worth respecting. Take two light sources per person, tell somebody where you are, and check the authority's page before you go: entry can close on water levels and on bat protection seasons.
Other places on the map within a couple of hours.
