• WHERE Central Otago, New Zealand
• HOW MUCH $1,200 for a fully supported tour
• MORE otagocentralrailtrail.co.nz

GETTING THERE Fly to Dunedin, a city on New Zealand's South Island whose architecture was influenced by 19th-century Scottish settlers. From there, take the historic Otago Central Railway through the Taieri Gorge, featuring 40 miles of steep slopes and vertiginous views. The railway ends at a town called Middlemarch, which marks the beginning of the Otago Central Rail Trail: a car-free, gently sloping 92-mile path that takes the average cyclist three days to finish. The trail runs along an aptly named mountain range called the Remarkables, which in autumn is blanketed in warm shades of yellow and red.

BEST MOMENT Waking up at dawn at the Wedderburn Cottages (one of at least half a dozen working farms that accommodate cyclists along the trail) and watching fifth-generation rancher Stuart Duncan whistle to  his bearded collie to round up the sheep.

FAVORITE CHARACTER Stuart's flannel-clad father, Graeme, initially opposed the rail trail, because he didn't want scraggly mountain bikers tearing past his ranch—he felt protective of his land. The reticent sheep farmer now says he enjoys meeting people from all over the world at the ranch's lodge, since most visitors share his ethic of stewardship. Ten minutes after we cycled away, he chased us down in his truck to hand me a small item I had left behind in the room.

LOCAL LORE Pitches Store in Ophir is a six-bedroom inn along the trail. In the early 1860s, it was a general store for miners. After robbers targeted horse-drawn wagons transporting gold to Dunedin, brothers John and Samuel Pitches started sewing gold into horses' collars to hide it from thieves.

WHAT'S GREEN Seeing New Zealand's South Island by bicycle is about as green as it gets. No fuel required.

WHAT'S NOT GREEN The railway's diesel-electric locomotives release some emissions, though they don't belch smoke plumes like old coal-fired engines. And the flight is carbon intensive, so if you come from North America, consider buying offsets.

PLANET-SAVING OPPORTUNITIES The extra income from visiting cyclists allows small farmers like the Duncans to maintain their close-to-the-land way of life, so just staying with them helps. To deepen your green experience in New Zealand, go to wwoof.co.nz for volunteer opportunities on ranches and farms.