This was truly a weird place to visit, but extremely incredible. It takes a long time to get here as it's about 4 hours from Salt Lake City or a few hours from Boise. You will know you are getting close when you start to see the ground turn black. The nice thing about this park is that it was not crowded. The campground was not even filled up on a Saturday in August.
My imagination ran as I looked around at the surrounds and thought of what this place might have been like 2000 years ago during the last eruption. You could actually see the large vents (splatter cones) that were erupting ash and lava. What amazed me was the Inferno Cinder cone which was like a small mountain. We hiked up it. This mountain grew from the splatter cone just upwind from it. The thing is huge. Checkout my blog here to see a picture of it.
http://www.adventure-space.com/photos/clint_pollock/tags/Craters+of+the+Moon/default.aspx
Would I recommend to others to see this park? Absolutely. If you are in Salt Lake or Idaho its worth taking a drive up there to see it. The park is located in South Central Idaho.