Biking trails. Surrounded by rice fields and forests, Longtan has made a strong push to develop a network of walking and cycling trails radiating out from the community. Rent a bike or simply walk, meander alongside streams filled with fish and turtles, and look out across fields of terraced rice and taro. Especially nice just prior to the rice ripening.
Longtan is a nice place to spend a Sunday escaping from Taipei. You won't need more than 5 hours for it though.