No Clue

This is in a field by the Alpine Art Center. I have no idea what it is. It's about 9 feet tall. There are several configurations. One that looks like Stonehenge. So, I'm curious now.

My boy (18 year old Down Syndrome) was with me and I didn't watch him for about 15 seconds and then I'd lost him and he was on the other side of a shallow river with wet shoes and pants when I found him. Got to be more careful. When I call for him he can't/won't? answer back so it adds to the panic. So, when I look back at this photo that's probably the story I'll remember. Thankfully an OK ending.