My office is very near Washington Square Park in NYC. When the weather is warm there's almost always a band playing jazz in the park at lunchtime. As often as possible I'll bring a sandwich to the park and just enjoy the moment there, watching people walk by, listening to the music, staring up at the big trees swaying overhead.

Like you, I usually find myself refreshed afterwards, and often wind up walking back to the office excited to tackle something that I'd been dreading when I arrived in the morning.