SeekerSupreme

With six hours you don't need a cache near the airport. In Amsterdam you can be downtown in 20 minutes. Trains are frequent and inexpensive and take about 20 minutes. Go downtown, it's more fun, and there are many nice caches near the Centraal Station.

You'd think they would solved this by now -- a whole 7 years later. No, they have not.

I don't know what theory you are referring to, but these are two very different problems. The problem for the human is simply to look at data that's reported and presented to them (the solution) and verify whether that particular solution is valid. The problem for the checker is to find a valid solution among the universe of finds. This can be a very different problem. Let me give an example. Consider a challenge to find two caches that are exactly 1000 miles apart (or within 0.1 miles of 1000, say 999.9 to 1000.1 miles apart). You can see that if I provide you a solution: "I found GC12345 and GC23456 and they are 999.94 miles apart" it is very easy to verify whether or not that statement is true. However, if I provide you a universe of 10000 cache finds and ask you to find a pair in there that meets the requirement, it's like looking for a needle in a haystack. Very hard. Once you do find the needle it's easy to prove that indeed it's a needle, but actually finding it is a very difficult problem for the checker.

Three more for your list: DUS: There is a very active one at Dusseldorf Airpot: GC193BP. Nice hike from the terminal, with very clear directions in the cache description. Please add to the list. FRA: You list one cache, but I have visited another one that is easily done from the airport in under an hour with a free hotel shuttle bus: GCHWM1. Please add this one. INN: Innsbruck Airport has a TB Hotel in the parking structure: GC1FY5E LHR: There is a mystery cache that seems fun. GC243KB. I tried doing it but did not find, but others have since reported it there, so it must be there. Thanks for maintaining this list.