It is easy to see why folks who pay $18 just to look over the rim feel they overpaid. But there is a lot more here to see. Guided tours leave every hour at 15 minutes past until 3:15. Our guide, Steven, was not only quite knowledgeable but a very engaging tour guide as well. The one hour tour is a less than quarter mile walk along the rim but well worth it - encompassing both the history and the geology of the crater.