Well, it has to do with where the drops of water are, relative to where you are. But in fact, that's an extreme wide angle view, done by stitching about 8 cell phone shots together. So, it's a highly distorted view. To give you some idea, I was standing less than a foot from the curb at the time, almost at the sidewalk.
The knack is in developing an eye for what might be a good shot. Some people didn't even see the rainbow, walking in. After a while, everything you see is judged by how good an image it might make.