Shaft

While waiting for the subway to come, I boringly started looking around.  Above and behind, I saw that there was a shaft that vented up to the sidewalk above.  The bright sunlight created a shadow that fell below creating an interesting geometric shape.  

When you look at it, it becomes difficult to know which direction you are looking, or what end is up.  A couple of times, I looked at this picture and was confused what was happening.  Are we looking down or up?  It almost looks like a prison cell as seen from above.  

Shaft