Meet Millie. While other cats consider playing with a feather toy and running from the dog an adequate exercise regimen, Millie spends her weekends rock climbing.

It all started when Craig Armstrong found Millie at a Utah animal shelter called Furburbia, as he writes in a recent essay for BackCountry.com. "It took about four seconds to realize we were now partners and would be going on many journeys together," he says. And that's exactly what they've done. Millie even has her very own harness, leash and rope, Armstrong explained in an interview with Bored Panda.

We can't get enough of Armstrong's gorgeous Instagram pictures — mostly starring Millie, of course. Check out these shots of their outdoor adventures, and head on over to Armstrong's Instagram to see plenty more.