Big open green spaces [urban parks] in the heart of cities, like Ibirapuera Park in Sao Paulo and Central Park in New York.
Those are public open spaces where people flock at the weekend for a picknick, and serve as a playground area for children and to a sport or outdoor activities, with the family friends. Or just hang out with them, it´s up to you.
So, one can do a workout, jogging, in the weekdays to stop by, get a bit of fresh air and clear the head.
One can do his activity of choice [of your liking/preference], do a bit of reading, jogging around, yoga, dance, biking, skating, and ride a skateboard or skater [that is, roller skater].
All that in open, a go-to place when visitors want to feel at the backyard of the big city. As a plus, you can see nature, to be in the middle of trees, little monkeys and other animals of its diversified fauna/wildlife. Birdwatchers are often rewarded with the sightings of birds and songbirds as well (in the United States squirrels reside in such parks – in the Central Park – for instance).
It´s indeed an escape without actually escaping, many would say that it´s an oasis in the middle of a concrete jungle!
Well, this is a draft of sorts, I hope it gets close to what you meant. It´s open to improvements, of course; anyone can correct or give suggestions.
See ya around!