Water, that is. During the hike to the top it's important to stay well hydrated. Fortunately, at each pondok rest pavilion on the trail, there's large tank of free drinking water constantly being fed by pipes leading down from clean water sources high up on the mountain. The tanks are marked "Untreated Water", but the water is safe to drink. Thus, it's unnecessary to bring lots of heavy bottles of water along; one container will suffice.
