The Paradise Valley spring creeks — Armstrong's, DePuy's, and Nelson's — are three private, spring-fed jewels strung along the Yellowstone near Livingston, and they're the closest thing to graduate school that dry-fly fishing offers. Gin-clear, weed-lined, stable water with big wild rainbows and browns that get a long, hard look at every fly. You pay a daily rod fee and you book ahead, and in return you get glassy currents, PMD and baetis and trico hatches, and fish that will school you politely all day. It's flat-water, fine-tippet, on-your-knees fishing, and people save up for a day on it.

• Limestone