The Gem Mountain in "Katie Island Adventure" is a relatively unique place in the game. There is a dessert machine in it that is more important. If you want to go to Gem Mountain, you can complete the "Enable Gate" task first, and then you Will be able to explore the beach area of Gem Hill, but climbing to a higher place is not easy.
How to get to Gem Mountain on Katie Island Adventure
After completing the Enable Gate quest, you will be able to explore the beach area of Gem Mountain, but climbing to a higher place is not easy. You have two main options: fix the zipline from the Horror Swamp, or find a rocky surface and try climbing.
The most direct way is to fix the zipline through the mission Zipline Adventure. To do this, you also need to establish a fourth-level friendship with the Pachadog. After restoring ziplines from the beachfront resort to the horror swamp, you will be able to repair ziplines leading to the higher levels of Gem Hill.
You can also try to find a surface that is rough enough to climb. While this is not an "official" way, you can climb and rest on a small rock until your energy is restored.
Remember to interact with the quick travel mailbox here so you can easily return.
