If that doesn't work, try riding a bicycle. You can adjust the pace depending on how you feel, and see a lot more than you would on a regular walk. If you pack a lunch, you can go pretty far, relax in a nice place, and head back.
For bike trails, there is an effort to connect Maine to Florida called the East Coast Greenway: https://www.greenway.org/
Having used it myself, it's not continuous but certainly better than nothing.
You just leave the city and turn to any random small road and you can relax. My favorite are the farming land near Lublin. 30 minutes from the city center there are roads where you pass 1 car per hour :)
https://live.staticflickr.com/7264/6999476374_94c82f49dc_o.j...