I have this thing: It is definately a focal point. I am not sure how deep the cistern is so I can't really make any rational suggestions. I do know that conifers like this juniper are somewhat shallow rooted. So, obviously not my "Dr. Seuss" tree here, but maybe think about a topiery tree, like a round boxwood or something, or a group of smaller round shapes. However, they are high maintanance, you need to clip them around twice a year. (Sorry about the mess in the background).
