Touristy Shit to Do in Dc: Nature

I just moved to DC last month and hope to tackle a lot of the tourist destinations in the months to come. This list is for nature and parks. Please add your suggestions.
  1. National Botanic Gardens
    Done
  2. National Arboretum
    Tackled lightly. Need to revisit with the dog.
  3. Rock Creek Park
    Tackled slightly. Needs way more exploration
  4. Meridian Hill Park
    Done!
  5. Dumbarton Oaks
  6. C&O Canal
  7. Kenilworth Aquatic Gardens
    Done!
  8. National Zoo
  9. Theodore Roosevelt Island
  10. Great Falls