Leaving the buffalos in Custer State Park, we discover our 3rd national park : Wind Cave National Park. 

This one will probably not stay in our top 10, but exploring one of the biggest cave network in the world is exciting enough to try the experience. So here we go for an one and a half hour ranger guided visit. 

The only natural entrance to the huge network that stands behind our feet is just as big as a basket ball. The first explorers had to crawl in tunnels that wide for tens of meters, with no U turn possibility. Because of the differences in air pressure inside and outside, the cave really seems to breath.

Wind Cave is also famous for its boxworks. The world biggest number of them are here. They come from dust which once entered some faults in the soil, then became hard (just like cement), and stayed there while the rocks eroded. So we can say that these formations are even older than the cave itself !!! For a non scientist, they are just beautifull rock formation, as delicate as crisps.

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