The first issue is to find a map with marked hiking paths. I found none. The second issue; even Garmin Connect has literally no GPS courses mapped beyond Ubud centre. The third issue; coming down from the North are multiple but bridges on the contrary are quite scarce, so you might end up going up or down a stream from some kilometres before being able to cross it. All those constraints should not prevent anyone to go and discover the countryside and the mountains/volcanoes of Bali. The impossibly green rice fields, the jungle (and sometime pristine rain forest), the scenic rivers, the friendly people along the way, the fresh air up in the mountains, all are great rewards for the effort made. It is the second time after Lanzarote that I travel with sport gears and I do not regret it a bit. It is a new way for me to discover a region, far away from any touristic path. Hiking in Bali is meeting the true spirit of this island, if you ask me.
The first hike was around Ubud, the second one on the 2nd highest peak of Bali, the extinct Gunung Abung volcano. On the second hike, I did not meet a single tourist. The only encounter I did was on the top of the volcano. 4 Balinese from Denpasar were picnicking after making some offerings to the gods at the temple erected at the top of the mountain.