SANGJU, South Korea — In a country where bikes are either a poor man’s transportation or a weekend workout for spandex-clad racers, the longest and most highly engineered network of car-free paths in the world is being built through dense evergreen forests, down wildflower-lined river valleys and over steep mountain crests.

“If you like speeding fast you will need to train, but if you want to go slow, anyone can enjoy riding our paths,” said Moon-wan Sup, a South Korean high school teacher who has ridden the entire 1,677-miles of trails completed to date.

Construction of the multimillion-dollar bike network was met with widespread disdain a decade ago as an expensive attempt to appease public contempt over former President Lee Myung-bak’s controversial Four Rivers Restoration Project. That massive $20 billion bridge-river, levee-dam and wetland development drew widespread protests as a boondoggle approved without public input or adequate review to benefit the businessman-turned-politician’s former construction industry cronies.

But it’s hard to hate a bike path.

Especially one that provides peaceful passage through massive cities and snakes through bike-only mountain tunnels with smooth pavement, solar-powered air tire pumps, bathrooms built in the shape of bicycles, and even London telephone booth-style “certification centers” every 12 miles where riders can stamp the location’s logo in special-issue passbooks.

And so, although fewer than 2 percent of people in South Korea get around on bikes (compared to 49 percent of European Union residents), the bike paths that will eventually reach 3,106 miles are gaining popularity, both with recreational riders in South Korea and among a growing number of foreigners who are choosing bicycle tourism as a vacation.

The routes are dotted with newer guesthouses, cafes and restaurants catering to cyclists who need a comfortable place to sleep or a spicy rice and veggie bibimbap bowl, the country’s unofficial comfort food. Farmers, clerks and baristas were consistently welcoming during a recent tour; a gas station attendant insisted on handing cyclists milky-sweet coffee outside the small farming village of Seosan, and an innkeeper near Chungju woke before dawn to scramble up eggs from her chickens with carrots and kale from her garden.

The paths pass beaches and waterfalls, rice paddies, garlic farms, persimmon orchards and pagodas. They sweep under the massive carved Buddhas in misty cliffs at Gyeongju National Park and pass by the Sangju City Bicycle Museum, a 300,000-square-foot center where hundreds of families, many who drive or take a bus down from Seoul, gather on weekends to practice pedaling on a small track.

Although short sections of the South Korean routes share roadways with cars, they’re mostly traffic-free and newly built, unlike networks that connect roads and paths like the EuroVelo’s 15 routes covering 43,495 miles between Portugal and Russia, or the TransAmerica trail, a 4,227-mile route from Oregon to Virginia.

For rookies or foreign visitors who don’t want to find their own way, bicycle tour companies are increasingly offering guided vacations in South Korea. The first locally, bikeOasis Korea , has wide offerings. The Netherlands-based Cycle Classic Tours is among the foreign operators that have added South Korean itineraries to their traditional routes through the French Alps, Spanish coastline and Italian wine region.

“Opening up the countryside for recreational use has rightly allowed Korea to show off its spectacular scenery, landscape and culture to locals and the rest of the world,” said Wijko Farnholt at Cycle Classic.

Spotting an opportunity to combine business with his passion for cycling, Duk Young Lee opened Bikely in Seoul nine years ago to focus exclusively on touring. His shop’s shelves are loaded with headlights and spare tubes, handlebar bags and cargo racks, tool kits and padded gloves. He regularly ships high-end touring bikes to customers around the world. But for those who want a South Korean pedaling vacation, he also rents the entire kit.