This is from a short New York Times article entitled "Outer Beauty and Inner Peace":
One of the practices taught on retreats is mindful walking meditation, with the intention to feel stillness in movement and the movement in stillness. Outside in the morning when it’s cool, you can see deer, wild turkeys and many other birds. You can spend 40 minutes moving 50 feet, yet you feel as if you’re traveling into rich surroundings that invite exploration. And that feeling endures as you move inside to the meditation hall and gaze out through the huge windows that overlook the land. In that hall, the feeling of what is “inside” can merge with what is “outside.”The writer is referring to a retreat center called "Spirit Rock Meditation Center".
I would say that the sense of "inside" merging with "outside" can happen in any meditation hall and that walking meditation certainly helps facilitate that awareness.