The Mima Mounds are a few miles outside of Olympia and no one is quite sure what they are. According to Wikipedia they are uniformly distributed mounds of soil, 1-3 meters high. There are a variety of theories as to why they exist. Settlers first thought they were Indian burial grounds, but excavations show that there are no remains. Other competing theories include: gopher mounds, sea rivers, earthquakes, and glacier paths. They're in prairie land and I imagine in the summer they're quite beautiful. We went in the middle of winter during a downpour. We walked along the paths in between the mounds for awhile, but the rain and non-plant/non-animal life made our visit short. Really fascinating.