Mount Agung last erupted in 1963-64 and is still active, with a large and very deep crater which occasionally belches smoke and ash. From a distance, the mountain appears to be perfectly conical, despite the existence of the large crater. In 1963-64 eruption, the lava flows missed, sometimes by mere yards, the Mother Temple of Besakih. The saving of the temple is regarded by the Balinese people as miraculous and a signal from the Gods of their power not destroy the monument the Balinese faithful had erected.

There are two routes to climb up the mountain, one from Besakih which proceeds to a higher peak and starts at approximately 1100 metres and another which commences higher from Pura Pasar Agung, on the southern slope of the mountain, near Selat and which is reputed to take 4 hours. There is no path between the two routes at the top. Guides are available in Besakih. The climb from Besakih is quite tough. It is sometimes tackled as a single climb generally starting about 1000 pm for a dawn arrival at the peak and sometimes with an overnight camp about three quarters of the way up. It is far harder than the more popular Balinese climb up Mount Batur. It is not a mountain that needs ropes and not quite high enough for altitude sickness but adverse weather conditions develop quickly and warm waterproof clothing is required and should be carried. There is no water available along the route. Proceed through the temple complex then continue on a path that travels continuously upwards on a steep narrow spur through open forest and jungle most of the way. There is little potential to get lost until the route opens up towards the top where the correct route doubles backwards. Many climbers miss this turn and continue up a small valley which can be climbed out of with some difficulty.