princetown, west of there is a disused railway that leads to two disused quarry's and king's tor, a nice circular walk, dry underfoot and impossible to get lost in thick fog/snow/rain/hale. south of princetown is a fairly clear path to more abandoned workings, and nuns cross, which has an intresting combined tunnel and mine. you might have to break the ice because it is waist deep water!. i think the templer way goes from teignmouth to haytor and this is a good walk and clearly signposted, which other people have mentioned. there is a very easy small mine at haytor which is locked. i am not sure who has the keys now but plymouth caving group are the people to talk about this, and mines on dartmoor in general. most dartmoor mines are small squallid affairs, especially in winter though. their are some big shafts , and even a slate mine, but access can be a problem. the area south west of the warren house inn is another place full of holes and a very nice pub, also the woods around buckfastleigh. there's also caves in those woods and a radioactive mine so be careful! in the west at tavistock theres a nice canal walk as someone mentioned, and do not forget morwellham quay if it is open.