For you who want to know more about the trek route of mount Rinjani. It’s actually very simple. If you only have three days to spare, you can only go for a 2D1N trip and you have to choose between Sembalun and Senaru, since they are located on different sides of the mountain. So how do you choose between Senaru and Sembalun?
If you want to summit in the 2D1N trip, then you would be going via Sembalun, which features an easier climb (mostly flat) through the grasslands to the base of the summit. The down side is that you would be walking under the sun the entire time.
If you are absolutely sure you WILL NOT attempt summit in 2D1N, you should go through Senaru. This will take you through a steeper non-stop climb through the rain forest and a fairly difficult rocky climb in the last leg. But it’s a more beautiful and shaded route than Sembalun. You cannot reach the summit in two days if you go through Senaru though.
It would not recommend attempting summit if you are doing a 2D1N. While it’s possible, you’d be very rushed and more tired since you’ll have to do a lot of climbing on the second day.
If you are doing a longer trek, longer than 3D2N, then you don’t have to worry about choosing as you would be hitting both sides anyway. However, if you are wondering whether to start from Sembalun or Senaru, it probably comes down to when you want to summit. If you want to summit earlier in the trip, then choose Sembalun. If not, then choose Senaru.