South of the Sun Valley area, Hwy-75 runs across 60 miles of south-central Idaho’s rocky black lava flows. Halfway between Sun Valley and Twin Falls, 16 miles north of the town of Shoshone, the Shoshone Indian Ice Caves (208/886-2058, daily May-Sept., $10) present a series of lava tubes developed into a low-key tourist trap. Just west of the highway, their constant cool temperatures make a pleasant contrast to the often-scorching summer heat. (The “ice” in the name is created by air currents flowing through the tubes, causing subterranean water to freeze.) The only way to explore the caves is through guided tours, which take about 45 minutes. The gift shop and mineral museum, which features lava rocks and local wildlife, will satisfy anyone’s needs for tourist-trap trash (and I mean that in the best possible way).

Just down the road, Mammoth Cave (208/886-7072, daily summer, $10) is much more basic and undeveloped.

The only town along this stretch of road, Shoshone (pop. 1,488) is a ranching and railroad center that marks the junction of Hwy-75 with US-93. Some of its buildings have been constructed from local volcanic rock. Though it’s a fairly timeworn place, Shoshone looks great at sunset, when its steel water tower glows and places like the neon-signed Manhattan Café (208/886-2142) on the south side of the railroad tracks look especially appealing.