St Louis! Gateway arch making a rainbow!
They said this wasn't uncommon at all. The arch was so high it effected the air flow(its right on the bank of the river, too). and would cause arch made rainbows. If you look very closely at the arch to the left of the rainbow, you can see black dashes in the side of the arch. These are lookout windows. You can(we did) get a ticket and ride a wild trolley type thing up the inside of the arch and look out the windows. Nice View!!