There are a number of memorable geocaching experience we had. A particular one was definitely when we finished THE German puzzle cache "Enigma #1" http://www.geocaching.com/seek/cache_details.aspx?wp=GC448A. It took us 18 months to answer the questions and make sense of the treasure hunt maps. Then we set off to find the physical cache - and in the end we were successful. That was a really substantial undertaking.
Tanks for the cache & for reminding me on all our great geocaching experiences we had to Fore! - Fogg