We have lived in Spokane for more than 10 years and I have passed this Structure/Castle/Stonehenge thingy while driving on the I-90 probably 1000 times, always wondering what it was, but never finding it convenient to stop. Thanks to my New Year's Resolution, I took 20 minutes out of my day to change my life. I still don't know what it is, as there isn't a placard and it's not anything I've heard discussed in any conversation. I did a little googling with no results. I will look into it. For now, I am satisfied that my bucket list just got a tiny bit shorter.