Anyone who visits Java cannot fail to be impressed by the string of volcanoes which dominate the skyline of much of the island. I finally got round to climbing the first of the big ones in 1996 and before long I realised that with a little bit of careful planning I could get to the top of all 12 of the 3000m peaks marked on the Nelles map of Java before my rugby knee collapsed completely, a target I successfully completed in August 2003. Although no special equipment is required other than a good pair of shoes, a couple of torches with spare batteries (and a small kerosene stove for the longer visits), these are serious mountains and every year a number of Indonesians collapse and die on them; some wander off the paths, while others are not prepared for the cold nights where the temperature may fall to near freezing near the summits. For practical reasons, it makes sense to undertake expeditions in the dry season (roughly May to October) although all the peaks tend to cloud up during the day and the best time to reach a summit is probably at dawn - personally I do not enjoy climbing in the dark as many of the trails are in poor condition owing to overuse. The question of access/permission/registration to climb is a very grey area, in some cases, you very definitely need an official permit, in other cases you can just pitch up and go. For most of the volcanoes, there is a point at which you can register your presence and this obviously makes good sense from a safety point of view. In some cases you would be wise to take a local guide (usually these can be recruited on the spot for U$10 a day or so), for others a small group of 2 or 3 can climb independently, especially the more popular peaks where there are always crowds of Indonesian students (and their rubbish). NEVER go out on one of these mountains alone and always take sufficient water - in just a few cases water is available on the climb. Instant noodles are a staple of local climbers while it makes sense to take along high energy food items such as nuts, chocolate and bread.
CAVEAT - several of these volcanoes have craters of varying sizes in their summit region. In these cases 'summit' as in 'Puncak' in Indonesian implies an accessible point on the rim. The highest points may or may not be readily accessible for obsessionists and may even not be immediately apparent owing to poor visibility or because there will be several similar places. This reports represent sensible (?) recreational activity, if you are the sort of person who carries a GPS to measure how far you have climbed or hiked, you are a very sad person indeed.
The mountain fauna and flora of Java are very interesting - but the fauna wisely keep out of the way of the visitors. Of the flora the most famous is probably the Javanese eidelweiss seen here on Argopuro: 
But there are many others including this tree like shrub on Argopuro 
Travelling from west to east here is a short guide to each of them. I make no secret of the fact that the further east I travel in Java, the happier I become. Bondowoso and Situbondo are towns which are unspoiled by progress and the same is true of the volcanoes which become more spectacular and less visited...... 1. Gunung Pangrango (3019m, 2003) Easily accessible from the Cibodas Botanical Garden area, which itself is in the hills east of the Puncak Pass above Bogor, some 1400m above sea level. You need a permit to ascend from the park headquarters, officially 3 days notice is necessary but turning up before the office closes the previous day should be OK. Actually Gunung Gede (2958m) is a (rightly) more popular destination as it has a spectacular large crater. I climbed both in a long 13 hour day which ended in the dark - officially you cannot start to climb until 06.00. There is another (longer) approach possible from the Sukabumi area. In recent years the park has regularly been closed to climbers on occasions later in the dry season..... This is Gede viewed from near the top of Pangrango. 
And the situation reversed: 
Finally the Gede crater: 
2. Gunung Cireme (3078m, 2000) Cireme dominates the countryside south of Cirebon. Although it is not one of the higher peaks, the starting point at Linggarjati is barely 500m above sea level. The climb is unrelenting, even with a pre-dawn start, it is a very long day trip and there are few views and a not particularly interesting crater - this really is one for the dedicated volcano 'bagger'. The Hotel Linggarjati can arrange a guide. I have read that the climb can be made on the opposite from Maja above Majalengka, starting at 1100m. This would be a rather shorter route I guess. 3. Gunung Slamet (3432m, 1998) Java's second highest mountain is best viewed from the hill station of Baturaden which is just north of Purwokerto. It is also visible on a clear day from the north coast plains just about the whole way between Cirebon and Pekalongan. The main approach is from the east side from Banbangan .... This is a tough climb and the conventional arrangement is to start in the late evening for an early morning arrival at the summit so as to complete the descent before it gets dark again, the rangers for the forest reserve can be hired as guides, just whether it is absolutely essential to get a permit to climb is not clear! There is a small active crater, but the mountain is relatively isolated and the views are not that great. I have read that the climb can also be made from the north side starting at Guci, 1050m. This is Slamet viewed from Sumberharjo sugar mill near Pemalang. 
4. Gunung Sindoro (3138m, 2001) and 5. Gunung Sumbing (3371m, 2001) These twin peaks are separated by the Kledung Pass (1200m) where there is a conveniently situated hotel which can arrange for guides. There are small offices in the villages at the base of each climb where you should register. The lower slopes of both have now been cleared and are covered in tobacco plants. Both ascents are quite straightforward and each can easily be completed in a single day with a dawn start. On clear days the views across from one to the other must be magnificent, alas I managed to choose two (successive) cloudy days. Neither crater is particularly interesting, again these are for the volcano 'baggers'. Given the clouds it is not impossible that there are higher parts on the rim than where the paths terminate. I have read elsewhere that Sindoro can be climbed from the village of Sigedang above Wondosobo and this might be a shorter ascent. Similarly there is a path on the east side of Sumbing starting at Kajepit/Tepit where vehicles can apparently get to 1800m. This shows the twins viewed from the temples at Gedong Songo above Ambarawa. 
This is Sindoro viewed across drying tobacco near Temanggung. 
6. Gunung Merbabu (3142m, 1997) One guide book recommends climbing from Kopeng and I have read an account of a climb from that side, but to me the obvious ascent is from Selo, the col between Merbabu and Merapi. The path is not immediately apparent but goes from the south-east side of the village, best to ask the locals who grow vegetables on the lower slopes. It is a not too demanding climb, easily completed in the daylight and (on a clear day) the views from the top (no crater as such) are absolutely stunning, not just Merapi (south), but the steep drop to the north with Lawu to the east, Sumbing and Sindoro visible to the west and even Slamet on a clear day. While I was in the area, the previous day I climbed Merapi (2914m) also from Selo, a relatively short slog - the advantage of this route being its shortness and accessing the 'interesting' areas at the top. There is another equally popular approach from Kaliurang. Note that this is one of Java's most active volcanoes, it can be dangerous and the climb may be 'off limits' - respect local advice! This is the view of the two from the temples at Gedong Songo above Ambarawa. Merbabu is on the left with Merapi just visible behind. 
This is Yuehong and I at the top in 2005, with Merapi just visible behind - my second time here and her first. 
7. Gunung Lawu (3265m, 1996) This is one of the easier of the climbs (no guide needed) as the trail starts from Cemoro Sewu which itself is 1800m above sea level on the spectacular mountain road between Tawangmanggu (a good base, except at weekends) and Sarangan (also a possible base). It is very popular with the students as it is considered mystical/holy by the Javanese (the delightful temples of Sukuh and Ceto are on its slopes), the trail is not too steep and is readily completed in a day. There is no crater as such and the views are mediocre. 8. Gunung Welirang (3156m, 1999) and 9. Gunung Arjuna (3339m, 1999) These twin peaks are best climbed in a single expedition which will require a night on the mountain; sulphur gatherers work on Welirang and they have a 'camp-site' high between the peaks where is plenty of water available. I climbed the long, steep path from Tretes (on local advice in Malang) but I suspect that the climb from Sumberbrantas would be much more pleasant, I have seen a report that a path exists. Arjuna is an 'old' volcano, all that is left is a small peak, but the view from the top is absolutely stunning - across to Semeru to the east and the other volcanoes round Malang to the south. Welirang is slightly active but less spectacular, there is an indistinct path between the two peaks which avoids descending to the 'camp-site' but my guide did not know it well enough..... This is a view of Arjuna (left) and Weilirang (right) over the pollution of Malang from the easily accessible Gunung Penanjakan (2774m) above the Bromo crater. 
10. Gunung Semeru (3676m, 1999) There are actually several other minor peaks in this area over 3000m but they pale into insignificance compared to Java's highest mountain, a spectacular cone which belches ash and smoke at intervals of between 15 and 40 minutes depending how active it is in any given year. This is a both a trek and a climb which starts in the village of Ngadas, itself well over 2000m above sea level. Conventionally, you trek to the base of the final ascent on day 1, camp overnight before completing the climb and returning to base on day 2. The side of the cone itself is covered in a mixture of pumice and small rocks, two steps up and one step (or worse) sliding down is the rule which will leave you exhausted at the summit - there are more memorial stones here than on all the other mountains put together. Do not attempt to get close to the actual crater - several tourists have with disastrous results - and do not try to ascend/descend the southern slopes. To get to Ngadas there is a road from near Pasirian (Lumajang) which may be passable to normal vehicles, most visitors charter a 4wd vehicles from Tumpang east of Malang. If you have plenty of time then spending a few days trekking in from Gunung Bromo to the north would be a pleasant option. This is a well known view of Semeru (across Bromo) from Gunung Penanjakan (2774m): 
However, it just as impressive viewed from the road from Malang to Lumajang which skirts its south side. 
11. Gunung Argopuro (3088m, 2003) This view of Argopuro (with Raung faintly visible behind) is taken from Gunung Penanjakan (2774m) above the Bromo crater: 
This is very definitely a trek as well as a climb, best done from Bremi (about 800m asl) to Baderan (400m asl) - there are small buses from Pajarakan (east of Probolinggo) to Bremi and minibuses from Besuki to Baderan. I left my car with the police at Bremi and they also found me a guide. I have to say I found this the most interesting of my trips, there is a wide variety of mountain vegetation including open meadows and the climbs are not too demanding. Leaving Bremi in the morning will allow you to camp out at the second (drinking water) stream from which a path leads to the actual summit. I was told Argopuro was not a true volcano, but there is a small crater here and some activity. There are excellent views to Raung and other mountains to the east. 
You have to retrace your steps to the campsite, but with an early start it should just be possible to get to Baderan before dark - you should be able to beg a bed for the second night here. Unfortunately, the area above Baderan has suffered very bad deforestation in recent years. If you have time to spare, the Hiyang plateau to the south also has some excellent walking, even some small ruined temples (I am told). 12. Gunung Raung (3352m, 2002) Gunung Raung lies east of Bondowoso on the edge of the giant ancient Ijen crater. This is pure volcano climbing at its very best. After checking in at the base 'office' at Sumberwringin with my guides, I climbed overnight to the rim (strictly, the true summit is on the far side and unreachable by this route) and back down again for dusk, it sounds quite simple but it is a long trek/climb. We saw no-one at all the whole way - the fact it was the day of the football world cup final may have had something to do with it. At nearly 1km, Raung has the widest crater of any of the big 12 and sitting almost alone there on the edge of it just after dawn was a magical experience. To the west, Argopuro and Semeru rose out of the clouds, beyond lay the others described above.
So why did I do them all? Because they are there, of course. However, after nearly 30 years of visiting Java, I have long since given up any hope of fully understanding what makes its inhabitants tick, but the strength of the island's culture comes in no small part from the mysticism associated with these fertile symbols. Struggling to the top of the last of them at the age of 55 was a humbling experience. I wonder how many other people have been up them all and I hope these notes and pictures will encourage others to follow.... I have lately discovered this locally based group who are into the same sort of thing In 2005 I met a group of young Indonesians students at the top of Merbabu who were using their holiday to climb each one in turn!
For those less energetic, there are other more accessible volcanoes. You can drive to the edge of Tangkuban Prahu near Bandung, similarly the edge of the main crater at Bromo. The walk to Bromo is a gentle stroll while the climb to Kawah Ijen from where the road finishes takes barely an hour. At Kawa Ijen - the steam comes from the sulphur springs and the panniers weigh about 60kg and have been carried up from near the lake. 
Collecting the sulphur as it flows liquid from the pipes. The atmosphere is stifling... 
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