Outside in a natural space: parks, forests, wild spaces, gardens, your own backyard. As long as you have the open sky above you and natural beings around you, you’re good to go.
For the city folks out there who might have a hard time finding a wild space or who live far from a park, try your best to find a place that feels natural and that you are attracted to. Even walking in a neighbourhood with a lot of trees and gardens will be good for you. Try to take the time to bike, run, or commute to a natural space as much as you can during this challenge.