A challenge cache requires geocachers to complete certain tasks (e.g., to find other geocaches meeting certain requirements) before they can log it. Typically, geocachers must send email to the challenge cache owner providing evidence that they have completed the challenge requirements, and the cache owner replies with the coordinates of the cache.
- County, Quadrangle, and Similar Challenges
- Fizzy Challenge caches
- Jasmer Challenges
- WASHINGTON CHALLENGE CACHES (bookmark list)
- Challenge Caches (Groundspeak knowledge base)