Black Magic Canyon is a little-known wayside on the road to the Sun Valley ski resort, and just a short drive from my home. Carved by the Big Wood River in the dark basaltic lava flows that cover the Snake River Plain, the canyon is only accessible when the Magic Dam's spillways are shut at the end of the irrigation season. It's a rugged walk among gorgeously carved rock formations, culminating in a short section of the bleakest, dankest slot canyon I know of.