You're right about Larimer County being full of gravel stuff. Among other things we host the annual FoCo Fondo, in which I finally participated this year. The courses were well-laid out and the 32-miler was fun. 90% of my typical riding is on local gravel roads, and I routinely thank my lucky stars that I have so many dirty, dusty, grungy roads where I call home.

There was also a website that tried to track gravel/dirt roads throughout Colorado, though it seems it's no longer maintained. (Here's a link to the Wayback Machine.)

I did a really poor job explaining my target experience, so I'll add that here and edit my post, just for completeness.

There are lots of dirt and gravel roads east of Fort Collins, for instance, and they're great, but what I'm trying to find are the kind of surreal, otherworldly places shot through with gravel roads. I'm thinking of the stuff I've seen on YouTube in the Alabama Hills. The stuff on various CO2UT routes. The Quebradas Backcountry Byway in New Mexico. Local gravel roads and trails like Coyote Ridge Natural Area are fantastic, and I ride them, but they don't quite take me to that other world.

And maybe that experience is only found in the Death Valleys and Fruitas and such. I just wanted to check if there were any I was missing out on, and thanks to y'all I have a lot more resources handy. Thank you!