I didn't leave it in a Natural Park as it is very hard to find Traditional Caches inside National Parks. Earth Caches, Virtual Caches and Adventure Lab caches are in National Parks but there's no physical container to leave a TB behind in. I did take it along with me to do an Adventure Lab Cache along the C&O Canal, which is part of the National Park System.
I left this cool TB inside a mystery cache at Rachel Carson. The mystery cache isn't a hard one to figure out, and gets a good amount of hits, so hopefully someone will pick it up and move it on soon.