Guna Caves!
A large tunnel network existed in a mountain of earth that protruded a couple of kilometres above the usual ground level of Sumatra Continent. This mountain of earth was flat like a board and seemed to stretch forever. At its longest, it spanned a length of 1000 kilometres.
Even its narrowest region still spanned a breadth of 200 kilometres, being a large landmass littered to the extreme with caves. The tunnels resulting from these caves caused a bludgeoning maze, unable to be mapped through.
Most people and Pranic Beasts stupid enough to enter the Guna Caves would be stuck roaming through the place forever due to the gravity within acting wonky.
Oftentimes, what someone thought was the ground in the Guna Caves might not be parallel to the ground outside. They might be at an incline, a cliff, or even upside down. The individual stuck in the Guna Caves wouldn't be wise enough to know it.