Could this be our tunnel??
"Weeble" sent me this link, but it looks WAAAAAAAAY too short (though Leslie tells me it wasn't really as long as I thought it was . . . . )
Maybe "Ken H." can look and see if my re-calculation of his waypoints/route could've taken us through this tunnel. I don't remember seeing the exit/keyhole of light so clearly when we entered, but perhaps it was the dark glasses and the bright light outside. Seriously, it seemed more like a mile long!