LEO LO MAN-KUK'S brand of hiking isn't for the fainthearted. While exploring Lantau's Yellow Dragon River with two friends, a storm erupted in the hills north of Sunset Peak. It was getting dark and the heavy rains quickly caused the river to overflow, catching Lo and his friends unawares. Visibility was poor. Each had to grab hold of a tree to avoid being swept away. 'We stayed up all night,' says Lo, a technology consultant. 'If we had fallen asleep, we would have fallen into the river. The water flushed away our food. I had no map, no compass. All of it was washed away. We thought we were going to die.' But the rain eased in the morning, and the hikers eventually found their way out. The close encounter hasn't deterred Lo and his friends, who have been exploring hidden Hong Kong since the mid-1990s. Often guided by only word-of-mouth tips, sketchy maps and compasses, they have documented more than 100 original trails. The results of these explorations, with directions and photographs, are posted on their website, www.hkadventurer.com , which has attracted more than 141,000 visitors. Groups such as Lo's are an alternative kind of grass-roots organisation. Residents who value Hong Kong's natural landscape over its skyline, they're keen to share their knowledge. They offer more in-depth information than government programmes, which generally stick to well-worn trails. 'Hong Kong is small, but it has some amazing mountain landscape to explore,' says Lo. 'In China or the US if you want to explore some remote area it will take you one or two days just for travel. But in Hong Kong it's just two hours on public transport. You can find some exotic, very remote, very dangerous places if you want to.' Other groups and individuals give the lowdown on Hong Kong's green treasures through similar websites, although few are as focused on its isolated, hidden corners. Information technology executive Daniel Chan Yuk-ming has documented and photographed a variety of waterfalls across the territory. Writer and photographer Martin Williams started www.hkoutdoors.com , which features some of his favourite nature spots, including Ng Tung Chai waterfalls in Tai Mo Shan Country Park, southwestern Lantau, and the northwest corner of Shing Mun Reservoir. A founding member of the Keep Lantau Beautiful group, Williams says the website is aimed at publicising the natural beauty of the environment and helping keep it safe. 'The key goal is to introduce some of our great places outside the city to overseas visitors and to local people and give news about various threats to these environments,' he says. Efforts of hiking groups such as Friends of Tai Long Wan (their motto: 'Take nothing but photographs, leave nothing but footprints') have helped implement strict building controls in those rare, pristine spots, Williams says. 'Other areas, too, perhaps need fans to protest planned developments,' he says. 'If local people can earn some revenue through tourists - restaurants, hostels, etc - maybe they'll be supportive of measures to conserve and even enhance the local environment.' Residents are making greater use of Hong Kong's natural assets. Seventy per cent of the land area is undeveloped, with 400 of the 1,104 sqkm designated 'protected areas', including nature reserves. According to the Country and Marine Parks Authority, about 12.2 million people visited country parks in 2004, up from 10.7 million in 1997. These sights get little attention from the tourism authorities. Hong Kong Walks, a pamphlet issued by the Tourism Board, is dominated by city tours. And unlike its other visitor guides, the board charges $80 for its publication Exploring Hong Kong's Countryside. But the board may be catching on to the rarity value attached to the blend of city and nature. Last year, it added the wetland park in Yuen Long to the itinerary for a group of travel industry executives. The board plans to 'continue working closely with the overseas and local travel trade to step up promotion of the green side of Hong Kong' this year, a spokeswoman says. Groups such as HK Adventurers prefer the less-trodden paths. One of Lo's favourite spots is Man Cheung Po gully in southwest Lantau. 'It's not too easy, not too difficult,' he says. 'And there are a lot of natural pools to swim in.' His most unforgettable trail remains Yellow Dragon River. His adventure there a decade ago is still a vivid memory. 'I've been back four or five times,' he says. For Eugene Tso Yuk-keung, another member of the HK Adventurers, the trek along Feng Bi Stream, on a trail leading up to the top of Lantau Peak, is one of the best. If you time it right, you get to see a beautiful sunset, he says. He also recommends the walk to Sheung Luk stream in east Sai Kung, for its picturesque waterfalls. Fellow hikers regularly look up the group's latest discoveries whenever contemplating more off-beat treks. More unusual requests have come from reporters seeking details about a track along which hikers died. The most interesting call Lo received came from a German printing company. Staff members had come across his website, and were particularly taken by a photo of a rainbow arcing across hills in the New Territories. 'They wanted to use the picture for the cover of their Bible,' Lo says. Meanwhile, Lo's hiking adventures are taking place further afield. When on business in Taiwan, the mainland and elsewhere, he often explores new tracks, either on his own or with local friends. 'I won't follow the map or go with tour groups,' he says. 'That's no fun. In many cases the routes don't exist on the map. You have to find your own way.'