Go to Germany or France and any self-respecting woodland walk will have exercise stations, usually made out of tree trunks. In Spain many costal promenades have them made from steel pipes set in concrete – see images.
Not so in the UK (with one exception being the trim track at Gateshead stadium – is it still there?), so it was good to stumble upon this article – “Urban Gym: an outdoor workout in the heart of the city” – in the Guardian on using street furniture as part of your workout.
This seems to me the most natural way to exercise, especially when you remember we inhabit bodies built to the “hunter/gatherer Mk1” specification.
“Urban gym” in France
Urban Gym in Arrecife, Lanzarote