National Park Service sites with "unique" experiences

[SSLPhD]

Please share some of the unique experiences that NPS sites have to offer.  This is not limited to national parks.  Preferably free, preferably not concessionaire-run.  Unique is in quotes, because some things are available in two (or 3? or 4?) parks; that's fine.  Please do not include hikes or views, unless there is something unique about the hike itself (perhaps Angel's Landing in Zion qualifies).  I will try to wikify submissions.

Here's a start:

FRUIT, NUTS, and BERRIES

Bryce Canyon NP, pine nut "sampling," Oct-Nov
https://www.nps.gov/brca/learn/nature/pinyonpine.htm

Capitol Reef NP, variety of fruit, late spring through mid-fall
https://www.nps.gov/care/learn/historyculture/orchards.htm

Great Basin NP, pine nut gathering, fall only
https://www.nps.gov/grba/planyourvisit/pinenutgathering.htm

North Cascades National Park Complex, apple-picking in the fall
https://www.nps.gov/noca/planyourvisit/buckner-orchard-loop.htm

[SSLPhD]

BOATING

Congaree NP, ranger-guided canoe tour
Voyageurs NP, ranger-guided North Canoe tour