When I was in Guanajuato last fall I saw a few postcards that showed a view of one of the tunnels under the city with some buildings hanging over the edge. I asked a few people where this location was, and quickly found it. The tunnels under Guanajuato were originally created to help with flooding, so that the river could flow through them under the city. Over time, the water table has dropped and the tunnels are now dry and used instead for traffic. This has the pleasant effect of reducing traffic in the center of the city as the cars zoom through the tunnels under your feet.
After locating this particular tunnel entrance, I figured it would look pretty cool in the early morning with some light trails from cars going by. So I stationed myself in the correct place before sunrise, and waited for cars to go by. I think the photo turned out pretty well, I might have liked it a little better if some of the windows of the homes had some lights on, but I guess it was too early.