Trekking in Indonesia: the climbs worth the effort

Indonesia sits on the Pacific Ring of Fire, which means more than 120 active volcanoes and a landscape built for walking. Some treks, like Bromo and Ijen, are short night climbs that anyone reasonably fit can do. Others, like Rinjani and Kerinci, are multi-day expeditions through cloud forest and scree, and one, the Carstensz Pyramid in Papua, is a technical mountaineering objective that costs more than a car.

The common mistake is underestimating the heat and the altitude. A volcano that looks small on a map can gain 2,000 metres in a day, and the temperature at the summit before dawn can be close to freezing. The other mistake is going without a guide. On most Indonesian peaks a guide is required by the national park, and on all of them a local guide is the difference between a good day and a lost one.

The classic climbs

Rinjani is the best trek in Indonesia. The three-day, two-night route starts near Sembalun, climbs through savannah and pine forest to the crater rim, descends to the hot springs at Segara Anak and finishes with a pre-dawn push to the summit at 3,726 metres. It is strenuous but non-technical, and the views of the caldera lake and the Gili islands are worth every step.

Bromo is the easiest and most popular. You do not need to climb it: a jeep takes you to a viewpoint, and a short walk and staircase lead to the crater rim. The classic version is a night in Cemoro Lawang, a 3am start and a sunrise over the Tengger caldera. It is crowded, cold and unforgettable.

Ijen is a night climb to a turquoise acid lake and the blue flames of burning sulphur. The trail is three kilometres to the rim and then a steep descent. It is hard on the lungs and the knees, and the sulphur smoke can be choking. A mask and a guide are essential.

• Rinjani: 3 days, 3,726 m, strenuous
• Bromo: 1 night, jeep plus short walk
• Ijen: night climb, sulphur and blue flames
• Kerinci: 2 days, Sumatra's highest volcano

Rainforest and wildlife treks

Not every trek in Indonesia is a volcano. Gunung Leuser in Sumatra is one of the last places on earth where orangutans, elephants, tigers and rhinos share a forest, and the trek from Bukit Lawang is the most accessible way to see wild orangutans. Two days in the jungle, sleeping in a riverside camp, is a highlight of any trip to Sumatra.

Lorentz National Park in Papua is the other extreme: glaciers on the equator, moss forests and some of the most remote terrain in Asia. It requires a permit, a guide, a lot of money and a serious expedition. The Baliem Valley, also in Papua, offers gentler cultural treks between Dani villages and is a more realistic introduction to the region.

In Kalimantan, the Tanjung Puting national park is not a trek but a river journey to see orangutans at feeding stations. In Sulawesi, Lore Lindu has megaliths and forest trails. These are alternatives for travellers who want wildlife rather than summit photos.

Seasons, altitude and weather

The dry season from May to September is the trekking season. Trails are firm, views are clear and the nights are cold but dry. The wet season brings mud, leeches, slippery scree and closed routes; Rinjani in particular is often closed from January to March. If you trek in the shoulder months, start early and be prepared to turn back.

Altitude is a real factor on Rinjani and Kerinci, where the summit is above 3,700 metres. Symptoms of altitude sickness, headache, nausea and breathlessness, usually appear above 3,000 metres. Ascend slowly, drink water, and descend immediately if symptoms worsen. Do not push for a summit you cannot safely reach.

The temperature at a summit before dawn can be 5°C or lower, with wind chill. A warm layer, a hat, gloves and a head torch are essential even in the tropics. Porters carry the heavy gear on most organised treks, but you carry your own water, snacks and layers.

• Trek season: May to September
• Rinjani closed: January to March
• Summit temperature: 5°C or lower
• Altitude symptoms above 3,000 m

Guides, costs and ethics

A guide is required on Rinjani, Ijen and most national park trails, and it is the right choice everywhere else. Prices for a Rinjani three-day trek range from IDR 2.5 to 4.5 million per person, including porters, food and camping gear. Bromo jeep tours cost IDR 500,000 to 900,000, and an Ijen guide IDR 400,000 to 800,000.

Choose a company that treats its porters well. Porters on Indonesian volcanoes carry enormous loads for low pay, and the difference between a good operator and a bad one is visible: proper shoes, shelter, food and a fair wage. Ask how much the porters are paid and whether they have insurance. If the answer is vague, walk away.

Do not leave rubbish on the mountain, do not feed wildlife and do not take souvenirs from national parks. Rinjani has a serious litter problem, and the parks are underfunded. Carry out what you carry in, and choose operators that do the same.

• Rinjani 3 days: IDR 2.5-4.5 million
• Bromo jeep tour: IDR 500,000-900,000
• Ijen guide: IDR 400,000-800,000
• Ask about porter pay and insurance

What to pack and how to train

Pack layers, not a heavy jacket: a thermal base, a fleece, a windproof shell, hat and gloves. Add trekking poles for the descents, which are harder than the climbs, and shoes with grip for scree. A head torch, a water filter or purification tablets, and a small first aid kit complete the basics.

Train before you go. A volcano trek is a long day on uneven ground with a heavy pack, and the fitter you are the more you will enjoy it. Hill walking, stairs and squats are enough for most routes. If you are attempting Rinjani's summit, add longer hikes with a pack in the weeks before.

And prepare to be flexible. Weather closes trails, volcanoes erupt, and the best-laid itinerary can lose a day. The travellers who enjoy Indonesian trekking most are the ones who treat the mountain as the destination and the summit as a bonus.

Questions people actually ask

Do I need a guide to climb Rinjani?

Yes. The national park requires a registered guide, and the route is not safe to do alone. Book through a reputable operator with good porter conditions.

How fit do I need to be?

Bromo and Ijen need basic fitness. Rinjani needs good fitness and preparation, with long days and steep descents. Train for hills and stairs.

When is the best time to trek?

May to September, in the dry season. Rinjani is usually closed from January to March.

Can I climb a volcano with children?

Bromo is feasible for older children. Ijen and Rinjani are not suitable for young children because of the night starts, fumes and exposure.