Geocaching is essentially a planetary treasure hunt. You look for hidden boxes / cans / bags of stuff left by other people for you to find. Then you play packrat, you take something from the stash and leave something else to replace it.
We found all three of the ones we went looking for, though I didn't really look at the map before we went out looking for the first one. It was stashed at the base of a big hill. I parked us at the base of the big hill - on the opposite side. Even though the straight line measurement said it was only one mile away we had to walk five miles in and out to get to it, plus up about 800 feet. When we did find it, there was a convenient parking lot less than 1/4 mile away. Taught me to look at the map for the next one.
And that next one was "Beale's Cut" a historical landmark made in the 1840's to let horse drawn traffic make it through the Santa Clarita hillside. Hasn't been used for over a hundred years and was a big collapsed, but a neat thing to see. Somebody had actually plundered (destroyed) the cache that was there except for the logbook and the bag that originally contained the stuff, so we replaced it with a cache I had made up. I was going to look for my own hiding place but this was a good use for it.
Last one was the only one that didn't require a lot of hill climbing. Near magic Mountain there is an 1896 railroad bridge that is surrounded by a lot of new prefab housing (sort of looks out of place). Hidden somewhere behind it was the third stash of the day. Left a multicolor superball in that one, found a souvenir from the 1986 Canadian Expo, notable because jonasbagel had actually been to it.
By that point we were both sweaty and sunburned. It will never be this easy again as these were the three closest to the house, all within 5 miles of here. We will have to go farther out next time....