Niagara Falls has two main waterfalls, one on the American side to the left and one on the Canadian side to the right. I think the actual border is to the left of the rainbow here. The car bridge into Canada is called Rainbow Bridge. For the rainbow I wanted but never saw, see our son's photo from his trip there in June: https://365project.org/arthur2sheds/365/2017-07-22
Thanks so much for commenting on my photo of the two sides of Niagara Falls with a rainbow between them. We went high up on a tower to get this view.