Michael Cook of The Vanishing Point wrote about his experience exploring the depth of the tailrace of the decomissioned Toronto Power Company Hydroelectric Plant at the Niagara Falls. (Tailrace is the downstream part of the dam where water re-enters the river):
Imagine a tunnel more than ten storeys underground, a hundred years old, bricklined, wet, and completely inaccessible save by descending through a narrow slit in its ceiling thirty feet above the floor, and then returning up the same rope you came down.
Now imagine that this tunnel flows into Niagara Falls, emerging behind the pummeling curtain of water that nearly everyone in North America journeys to see at some point in their lives.
This tunnel exists. In the autumn of 2004, thanks to the work of two people with the experience and equipment to make it happen, I had the chance to feel Niagara Falls.