A multi area/part cache. Meaning when you get to the location there is some instruction or clue that leads you to a new location. I'd think only 2-3 parts limit or someone might get irritated. I've already done one myself but the 2nd part was in the same area. Got to the location, answered simple questions based on the area, this lead to decrypting the coords for the next location. In this case it was only about 100 feet away.
I'm thinking of setting one up that might be a few miles away and take an hour or 2. If that works out then something more complex that might take all day. The intend is for a small challenge and adventure, but not something so difficult there is a chance to fail. Optional an interesting quest story as well. 1 part at each location.
Do people like this kind of thing, or is it mostly get to a location, find the cahce in 5 minutes, move on to the next cache and see how many can be racked up in a day? Of course this would be indicated in the intitial description so anybody that wasn't interested could just skip it.