The rolling, grassy plains of southwest New Mexico are not an obvious place to find unusual, eroded rock formations but in one shallow valley near Deming, well south of though still in sight of the rugged Gila Mountains, is a half mile expanse of large volcanic columns up to 40 feet tall, known as the City of Rocks.
The area was incorporated as a state park in 1952 and is popular for camping, photography, wildlife watching or just walking amongst the rocks - some can be climbed, others have sheer sides that form a maze of narrow passages between them. The park is a favorite with children, who can explore the rocks all day, though the average non-camping visitor may only stay for an hour or so.
The park lies in the Mimbres River valley, half way between Deming and Silver City along US 180, then 3 miles northeast on NM 61 and 1 mile down a side road. The day use fee (2020) is $5, or $10/8 for camping, paid at a self-service entrance station, next to which is a short spur road that climbs 100 feet to the top of a small hill that gives a panoramic overview of the formations and the surrounding empty Chihuahuan desert prairie. The main road ends at a visitor center, astronomical observatory (the dark nighttime skies hereabouts make for good star gazing), desert botanical garden and the campground - this has 52 well separated sites (ten with electricity), some nestled in alcoves right among the rocks, all furnished with fire gills and picnic tables. The sites are distributed all around the formations, which are encircled by a 1.5 mile dirt track.
The rocks are light brown to pink in color, often covered by various shades of lichen, and eroded into many wonderful shapes and forms. They are the result of wind and water erosion of compacted tuff, formed by eruption of a nearby volcano about 35 million years ago. The eruption was from the Emory Caldera, centered near Hillsboro Peak at the southern end of the Black Range, and which has left other volcanic residues spread across 50 miles of this part of the state, including nearby Table Mountain, recently (2005) added to the park after being purchased from a local landowner. Little vegetation grows around the boulders, just the occasional oak or emory tree - between most are either bare, sandy chambers or narrow, slot-like passages.