One of the trips Bob got to go on for the 2022 Fall Arch Rally by the Natural Arch and Bridge Society was to a geologic feature called the Cosmic Ashtray in the Grand Staircase-Escalante National Monument, Utah. This is considered to be the largest natural pothole in the world. So, it was not a hike to a natural arch or bridge, but was still very interesting. The approximate dimensions of the Cosmic Ashtray are 200 ft (66 m) long, and 150 ft (45 m) at its widest. The central plug is about 33 ft (10 m) high. The dark orange heavier sand grains are blown in from the surrounding desert. The lighter grains eroded from the walls tend to blow out and don't remain inside.

For more information about arch rallies and natural arches and bridges, check out natural arches.org, the web site of The Natural Arch and Bridge Society.