The bicycle is the unofficial symbol of China, and with more than 300 million trundling about you'll have no trouble hiring anything from a rattly old local Forever brand to a half-decent multi-speed mountain bike. Even in towns that don't see many tourists, there are hire shops catering to Chinese who are passing through. Cycling tours are popular and many Chinese and Western travel agents offer short and long-term biking jaunts. Camping along the way is also possible if you can find a few spare blades of grass.
If it wasn't for the ubiquitous and ridiculously expensive permits, mountaineers, white-water rafters, hang-gliders and other adventurous types would be over China like a rash. Instead you're far more likely to encounter mountains of red tape. At least hikers can carry on regardless without having to obtain a permit, as they don't need much equipment. But opportunities for hardcore hiking can be limited as trails are fitted out with handrails, steps, souvenir vendors and restaurants. One solution is to go underground. Caving, particularly in the south-west provinces, can be a lot of fun - but be prepared to get wet and muddy.
Camel rides are popular in Inner Mongolia and in the deserts around Dunhuang (Gansu Province), and horse riding in the hills of Xinjiang and west of Beijing can be a beautiful way to spend the day. Winter offers ice skating on Beijing's lakes and skiing (downhill and cross-country) in the North-east provinces, but Westerners with big clodhoppers may have to bring their own boots.
More sedate pursuits include t'ai chi, a popular form of slow-motion aerobics practised in nearly every town park in the early morning throughout the land. Novices are always welcome. For brain exercising, most universities offer courses to fee-paying foreign students; possible subjects include Chinese language study, Chinese medicine, acupuncture, brush painting and music.