Whenever you can
Foamhenge is totally awesome. This is another spectacle that was closed when I passed through, but I was still able to see these enormous foam structures from the highway. I wish that I could have gotten up there to have tried to push over a few pillars, or to climb up on them. Man, thinking about it now, just makes me want to go back to. Witnessing what prehistoric man was able to accomplish with their ancient tools and technologies is quite captivating.