Choose the Sembalun or Senaru ascent routes.
Serious trekkers should consider staying on the Rinjani mountain for three nights or more with a planned trek that includes the crater rim, the lakeshore, the absolute summit, and more. Such treks normally start in either Senaru or Sembalun; however, in the last couple of years, some other routes have opened, including the Benang Stokel, Timbanuh, and Torean routes.
Senaru ascent route
This is by far the most used route, as it allows a relatively less strenuous trek to the crater rim. You start at an elevation of 600 m in Senaru village, normally in the late morning or early afternoon, and make the 6-hour ascent to the crater rim before dark. The first part of the trek is through the tropical rainforest. Look out for the lutung, or black monkey, swinging through the trees late in the morning. They are extremely shy, unlike the common macaques, which may gather near rest stops waiting for scraps. The route passes through POSII at 1,500 m, breaches the treeline at 2,000 m (POSIII), and then it is a bit of a slog up gravel paths to the campsite just below the crater rim at 2,600 m. There is no clear path at the last section nearing the crater rim, at an incline of 45 degrees. Porters have chopped up the remaining bits of the POS Extra, which was located after POS 3, for use as firewood.
If that has not sapped all of your energy, you can then make a very precarious descent down to the shores of the crater lake and bathe in the hot waters. You need some confidence to do this, as it is a steep descent of 600+ m using handrails and ropes. Then, you will return to Senaru using the same route you originally took. Local guides claim going down is faster, but speed varies for individuals. Patience is vital for first-timers, as it can get frustrating watching porters sail past you with their load balanced on one shoulder, clad in slippers, or even walking barefoot. Descenting from POS Extra to POS 3 can be slippery when the weather is dry, as scree tends to give way under your feet. From POS 3 to POS 2, the descent can take 1.5 to 2 hours as savannah grasslands fade away and the humidity and heat from the tropical rainforest begin to set in. Useful tip: request guides to cut out a wooden trekking pole if you did not bring one with you. It will be extremely handy during the descent, especially when the legs are aching from the strenuous climb. There is an option to continue to Plawangan II, where you can spend another night before making the ascent to the absolute summit. However, we don’t particularly advise doing this from the Senaru side. Sembalun is the best starting point for the climb to Plawangan II if you want to reach the top.
Sembalun ascent route
Starting in the morning from the Rinjani Trek Centre in the village, the climb to Plawangan II at 2,638 m will take about 8 hours via POSI (1,300 m), POSII (1,500 m), and POSIII (1,800 m). The starting altitude is 1100 m, so there are no humid conditions to deal with. The first half or more of the trek is literally a breeze. The trek through savannah grassland is windy and easygoing, with gentle ups and downs, and the only obstacle to look out for are the cow pats deposited by the villager’s cows along the way. Rolling hills and amazing scenery help to ease the tiredness, unlike the enclosed tropical rainforest of the Senaru route.
From POS 2 to POS 3, the climb is still manageable. The challenge for the Sembalun route is getting from POS 3 to POS Extra, as the uphill gradient can be 50 degrees at times. This section may pose a challenge for young children due to the spacing of some steps. Although the cooler weather up here may suggest that the body doesn’t require fluids, it’s important to drink more to prevent altitude sickness from setting in. Strangely, there is a guy selling cold drinks for those who crave them. Spend the night at the campsite here and begin your climb to the summit at 3 AM the following day. You need to be well-rested, as this is a stiff task. The final climb is nearly 1,100 m on difficult ground.