The imposing Arjuno-Welirang massif is located just 50 kilometers south of Indonesia’s second-largest city, Surabaya. Mount Welirang remains active and is still worked by local sulfur collectors, whereas Arjuno (also spelled and pronounced "Arjuna") is dormant.
Nestled between the two volcanoes are the twin peaks of Kembar. Traversing this entire massif is considered one of Java’s most stunning hikes. Due to its vast expanse, spending one or two nights camping is necessary.
If the weather perm...
Ascent from Sumber Brantas
Recommended for hikers in excellent physical condition
The most popular and well-defined trail starts from the mountain resort of Tretes (812m) to the north-east of the range. This route is particularly appealing for those looking to summit Welirang and/or Arjuno without wasting time, as it starts at a high altitude and leads directly to a pass between the Kembar peaks. At the top of the pass, hikers have a choice: head left (north) toward Mt. Welirang or turn right (south) toward Mt. Arjuno.
Sumber Brantas is 11km beyond Selekta and the hike begins either at the official village trailhead (1,655m) or further on at two cement pillars (1,750m) just before the road begins to descend to Cangar air panas (hot springs at 1,628m). The start of the trek is a farm track leading through fields of carrots and potatoes.
At 1,950m the trail enters forest and leads via Pos 1 (2,056m), Pos 2 (2,357m) and Pos 3 (2,570m). Pos 2 – which is marked with a large boulder – makes a reasonable camp spot for anyone who has started late in the day, and the Kembars are clearly visible in good weather.
Pos 3 is actually a better camping area and it is here you can take a left towards Welirang or right towards Arjuno
In the middle of the night, you head toward the fascinating crater area of Welirang (Kawah Jero), reaching its highest point at 3,156 m.
The trail is pleasant and almost flat, offering stunning views of the western slopes, particularly of Mt. Anjasmoro. Further along, a small path branches off to the left—this is the sulfur collectors’ trail. You should be able to spot them working on a steaming lateral crater, surrounded by sacks filled with large yellow sulfur rocks.
The trail to the summit of Welirang veers slightly to the right, passing an old dormant crater overgrown with vegetation on the left before crossing a rocky plateau. Here, many local hikers have left messages on the flat patches of volcanic sand using stones. Finally, you reach the summit crater—Kawah Jero—where sulfur fumaroles rise from the ground. A full circuit around the crater can be completed in approximately 30 minutes.
The two highest peaks of the crater offer breathtaking views of Mt. Penanggungan and, if you're lucky, a panorama of all the surrounding summits—from Mt. Lawu in the west to Raung, hidden behind Argopuro, in the east. If the weather is optimal at dawn, this vantage point is arguably one of the most spectacular on the entire island of Java.
Heading toward Arjuno, you will encounter, shortly after Post 3, hot steam rising from beneath the rocks in the middle of a pine forest (2,620 m). This forest ends at 2,875 m, revealing a breathtaking panoramic view. The trail soon reaches the summit of the pass (2,911 m) between the Kembar peaks, which is also an excellent campsite. This area is known as Lembah Lengkean.
The first peak to the south is Kembar Dua (Kembar 2)—the southernmost and slightly higher of the two, standing at 3,113 m. From here, you can enjoy a stunning panorama of numerous nearby and distant volcanoes. The area features shallow grassy craters and multiple sulfur vents, so caution is advised to avoid inhaling the gases.
Reaching Arjuno’s summit directly from this peak is challenging due to the steep and hazardous terrain. Instead, it is best to circumvent the eastern base of Kembar 2, following the safer and more commonly used route.
The first summit you will reach on the slopes of Arjuno is marked by a regional boundary marker (3,315 m). The trail then descends slightly before arriving at a broader peak. This "western summit" is very similar in height to the final summit, located a bit further ahead. Most hikers consider the latter to be the true summit, as it is likely one or two meters higher.
From the summit of Mount Arjuno, Mt. Semeru stands prominently right in front of you. The final peak, slightly further east, is narrow, striking, and scattered with rocks. This is actually the true summit of Arjuno (3,339 m), although the previous peak is also often regarded as the highest point. This narrow eastern peak is known among local hikers as "Ogal Agil".
Return to Pos 3 in the mid-morning, then descend to Sumber Brantas.
Ascent from Sumber Brantas
Trekking time : Between 5 to 8 hours per day
Difference in heights : +/- 1,685 m