Amboy crater is an extinct volcano only 1.5 miles south of Route 66 near the town of Amboy. The crater is estimated to be 79,000 years old with it's last eruption approximately 10,000 years ago.
It was designated a National Natural Landmark in 1973, and recognized for its visual and geological significance. Although this crater is not unique, it is considered an excellent example of a very symmetrical volcanic cinder cone.
The Bureau of Land Management suggests the following if you're planning a visit:
"The drive to get to the crater is astonishing and takes in the most amazing scenery, even if it's quite desolate at times. Probably best to visit with company as it can be quite a lonely spot, and be sure to take plenty of weather - the temperature at the height of summer is extreme. Plenty of great photo opportunities and sunsets are spectacular."