With the talk of the tunnel It reminded me of the area on the other side of the road that goes alongside the aquarium. It looks like it was a greenhouse or some type of cage area? Its all overgrown with vines. Not talking about the zoo. I know what that looks like. This is on the Canadian side.
Also my Dad has mentioned a sledding hill that was on Belle Isle that you could slide down and wind up on one of the ponds.
Can someone tell me what the "cage" area was though??
Add your own lost structure/formation.