If you're looking for the popular trad and sport area in Idaho, this is not it.
This is the other COR, and climbing-wise, it is a bouldering area, with some highballs since the boulders get up to 40' high though most are much shorter than that. If free soloing short Class 5 routes from moderate to hard is not your thing, you can also find plenty of Class 3 to low 5th scrambling.
And, of course, you can just hike the trails and wander among the boulders.
A quick stroll through the boulders will reveal massive potential for short sport routes, but before you grab your kit, know that park regulations prohibit installation of bolts and other fixed hardware. A few boulders have cracks and other features that would allow them to go on trad gear, but anchoring would be difficult. So, again, you're looking at bouldering and scrambling as your climbing options. The park service also prefers that you limit your use of chalk; it actually is rather nice not seeing this place all chalked up the way so many other easily accessible bouldering and sport-climbing destinations are.
About 35 million years ago, a huge volcano erupted here. That and erosion during the millions of years since created the landscape seen now. The "city" rises from a plain that for miles in all directions is largely featureless aside from desert scrub.
Most of the boulders are along or surrounded by a loop road that also is the way to access campsite. So, do not expect a wilderness experience here; you may top out on a boulder and find yourself looking down on someone's campsite.
Spring and fall are the best times here. Winters can be cold but will have many climbable days. Summers are very hot, and there is very little shade save that from the boulders themselves.
Between Silver City and Deming, leave U.S. 180 and head northeast for about 5 miles to the park entrance.
$5 per vehicle daily entry fee. Annual state park passes are available for $40. This information is current as of July 2019 and may change without being reflected here.
No bolts or other fixed protection! No chipping or drilling. Don't put chalk all over the place.
Mountain Project page-- Presently not much information here about specific problems, but better than nothing. The guidebook link does not work anymore. Just go out there and find something that looks cool and get on it.
There is camping along the loop road and one of its spurs. Some of the campsites are reserveable; see the park website for details.
At the visitor center you can find modern restrooms, showers, and running water.