Roadtripping through Idaho and Montana is sublime

IT'S POSSIBLE that you've never heard of Boise, the state capital of Idaho, yet it's a vibrant and diverse city full of green spaces and great bars and restaurants.

Boise is a good starting point for exploring the splendid Rocky Mountain scenery that surrounds the city - point your steering wheel north and venture on a 305-kilometre drive to the iconic Idaho mountain resort of Sun Valley.

En route pass one of America's chilliest towns, Stanley (annual average temperature 1 degree Celsius) before topping out on 2,652-metre Galena Pass in the evocatively named Sawtooth Mountains. Stop to admire the serrated ridges and peaks before dropping down to Sun Valley, holiday home of movie glitterati such as Tom Hanks, and the associated town of Ketchum - once known as Leadville for its lead mining connections and later as the largest sheep-ranching centre in the West.

It's worth spending a day to hike in the nearby Sawtooths; or stay locally and take a ski lift to the summit of 2,788-metre Mount Baldy, where one can walk or mountain bike on dusty trails that in winter become some of North America's longest ski runs; or just enjoy the views.

Next day head east on the 358-kilometre drive to West Yellowstone, crossing the bizarre Craters of the Moon lava field. Drive right through the lava formations and stop-off to see the surreal cornucopia of cinder cones, spatter cones, lava bombs and tubes is a must.

From here cross the arid Snake River Plain to the town of Idaho Falls (look for the "wedding cake" Mormon temple in passing) then start climbing back up into mountain country on US Highway 20 crossing into Montana at 2,155-metre Targhee Pass. If time permits take a short detour to the spectacular 34-metre torrent of Upper Mesa Falls; it's not the end of the world to miss it as one soon hits Yellowstone National Park with enough natural phenomena and scenery to blow your mind.

West Yellowstone reveals time-honoured spectacles such as Old Faithful geyser (which blasts up to 30,283 litres of superheated water up to 55 metres every 91 minutes) and roadside wildlife like elk and coyote.

The next leg of the drive is the longest - 434 kilometres from West Yellowstone to Missoula - so get an early start as there's plenty to see along the way. The journey north along the Gallatin Valley is glorious - the setting for Robert Redford's film A River Runs Through It - and it's commonplace to see fly fishermen at the river's edge and even a moose or two supping from the river banks.

Stop for coffee or lunch at the stylish Gallatin Gateway Inn on US 191, a former railroad hotel just south of the university town of Bozeman, or try the art deco Baxter Hotel on Bozeman's Main Street. From here head northwest on Interstate 90 past the former mining town of Butte, once called "the richest hill on earth" for its immense silver and copper deposits.

Things are considerably quieter since the mines closed in the 1980s, but there's a strangely compelling attraction to the town and the massive toxic pool of Berkeley Pit, once the largest open-pit copper mine in America. It sits oddly with the surrounding wild landscapes on the way through the Garnet Range to Missoula.

Spend a day in this leafy town before continuing north on US93 to Whitefish through yet more lovely mountain scenery and past the occasional buffalo ranch. On the way encounter the blue waters of Flathead Lake, the biggest natural body of freshwater west of the Mississippi. Since the drive is only 198 kilometres there's time to enjoy the water at the town of Polson, in a rowboat or passenger steamer, or swim at one of the lakeside beaches.