I was trolling through HikeAZ to find fun hikes and interesting things to see off Hole in the Rock Road when, Hey!, there were triplogs and photos of “The Cosmic Ashtray”. My focus was intensified immediately. You could have dropped a small bomb behind the desk and I might not have noticed. We love bizarre and other-worldly sights.
The Ashtray became a “must do” highlight of our trip. We met up with some friends the night before and set an AIS time (“arse-in-seat”) for the following morning.
The hike is 8+ miles round trip. All that we'd read in advance was about the Ashtray itself and didn't describe the hike from our chosen approach. Thankfully we found a GPS route to download. The hike starts out along an old jeep trail. Rather nondescript and a bit of a slog at times. But, after about a half mile, you abandon the road and strike out across sand and slickrock to the west.
There is no trail nor any cairns to follow. Just keep the base of the slickrock "hills" to your south. We attempted to maintain a contour line so as not to ascend (or descend) for no reason. The views of snow-covered peaks and enormous alcoves are plentiful. The Straight Cliffs and, usually, Navajo Mountain are ever-present. You'll see thousands of Moqui marbles along the way.
A little over three miles in you start heading directly south, still keeping the sandstone peaks to your right. You'll notice odd chunks of black, volcanic, hollow-sounding rock scattered across the quilted, orange slickrock and veins colored nearly purple. At about 3.75 miles, you'll get a glimpse of the highest lip of "the stadium". Keep working your way across the sloped slickrock towards the stadium. A quick scramble up the slickrock and "Wow"! I'll let the photos, as unprofessional as they are, speak for themselves.
An article from Smithsonian.com explains the formation of this (un)earthly wonder.
Return the way you came. Or, if pre-planned, you could make a shuttle out of it by leaving a vehicle at the Harris Wash trailhead.
Check out the Official Route and Triplogs.