There is a county owned public airport for small aircraft on the border of El Cajon and Santee in San Diego county. While researching geocaches around Santee, specifically around Prospect Ave, I found out there was what is called a virtual cache located there. These caches aren't a physical container, but a location that will draw your attention to see some place of note. With these caches, you are asked a few questions about what you see at that location and email the answers to the person who placed the cache.
I won't list the questions or the answers for the cache, but here is the link to the cache page at geocaching.com.
The cache is called 3..2..1. The place to where we were led was the Gillespe Field Annex of the San Diego Air and Space Museum. I did not know it was there. On the grounds are a number of historic aircraft and exhibits. It didn't take long to check them out, but it was pretty fun.
If you are out there, especially with kids, you should check it out. It's free and open Monday, Wednesday thru Friday from 8:00 am to 3:00 pm.