We found ourselves this morning hiking the south side of the park. The dunes are more open and create quiet valleys. It's a beautiful part of the park and much less traveled. As we approached the lake we came across this old, large concrete structure. While it doesn't appear to have a proper entrance, it does have 2 large holes on top -- one of which is plugged with concrete, the other is open with no ladder to get out if one should decide to take a trip. We're not sure what this is but we suspect it might be part of an old water tower or cistern. Looks like a bunker to me. Remnants of a water system can be found throughout the park. Not sure if anything is still in operation. Behind the structure, up in the tree, are large pieces of rusted scrap metal.