Our youngest boy has been giving roundabouts scores out of ten since we drove to France when he was very little. Scores relate to everything from roundness, to flowers, to originality to how tidy they are or whether they are wildlife gardens.
Brussels has amazing roundabouts, they help to navigate as well, huge fountains, statues, copper crocodiles and frogs playing instruments, pictures made with sedums, there is a surprise at nearly every one!
For me though, the best show offs are France during the tour de France...amazing, bright, cheerful and so neat, all sponsored of course. I also love newly built roundabouts that are liberally covered in wild poppies and flowers where the top soil has been disturbed.
Dh used to hitch hike with a friend during his mis-spent teenage summers, they can list the roundabouts they have camped on en-route to sunny cornwall or Dorset.