Anvil Points Claystone Cave is an unusual and genuinely adventurous cave on the west slope of Colorado near Rifle, tucked into the arid hills just north of Interstate 70 out toward the little community of Rulison. Unlike the limestone and lava caves that dominate most caving lists, this is a claystone cave, carved into soft sedimentary rock, and it offers about 2,500 feet of passage that ranges from tight crawls to genuinely large walking corridors. For prepared, experienced cavers it's a distinctive underground trip; for everyone else, it's a place to understand before setting out.

The cave has real character. Inside, the passage varies dramatically, from tight crawlways to big rooms measuring something like 60 feet tall and 40 feet wide, a striking range within a single system. It's also strikingly cold, holding around 55 degrees while the surface bakes near 100 in summer, and it breathes: there's a notable wind moving through the cave, which is part of what makes descending into it such a memorable contrast with the desert outside.

Reaching it is a modest effort, about a half-mile hike from the road, with the cave located roughly 2 miles north of I-70. One important practical caution: the usual parking near the oil pad on the west side of the road is likely private property, so it's worth sorting out legal parking and access before you go rather than assuming. This is working energy country as well as caving country, and respecting land status matters.

Caving here demands the standard serious-caving kit and mindset. Bring at least three independent sources of light, a helmet, and dress for a cold, windy environment; claystone can be slick and messy, and a 2,500-foot cave with tight crawls is no place to be under-equipped or alone. Never rely on a phone light, and let someone know your plan and expected return.

The cooler months and shoulder seasons are the most comfortable for the surface approach across the exposed west-slope hills, while the cave interior stays cold and windy year-round, so layers are essential no matter the season. There's no water and little shade on the approach.

Come with a helmet, multiple lights plus spare batteries, gloves, warm and cave-worthy clothing you don't mind getting muddy, sturdy boots, and a partner. Sort out access and parking ahead of time, tread carefully in the fragile claystone passages, and take nothing but photos. For experienced cavers looking for something genuinely different in western Colorado, Anvil Points Claystone Cave is a memorable and unusual underground adventure.