Far beneath the ground from which the towering structures of the Iwagakure rise up, there is a vast underground network of caverns and passageways which have been a part of the village for generations. Despite the utter destruction of the village above, the Underground Caverns remain relatively unaffected. Had the village anticipated the severity of what was occurring earlier, there is no doubt that the entire village could have been evacuated into the caverns with relative ease to provide safety from the attack.
The caverns themselves are the product of the waterfall cliffs above which have fed the caverns with water for thousands of years, carving out the caverns as well as supplying them with miles upon miles of fresh water sources. The caverns themselves are legendary and are well known for their immense resistance to earthquake activity and all other forms of damage. To many, the caverns themselves were a point of pride within the village, giving many the feeling of 'natural' security as the walls and ceilings of the caverns seemed impervious to cave-ins.
The passageways themselves extend for miles and are incredibly spacious, with ceilings over 100 feet above the ground in many cases. However, the network of caverns can be somewhat hard to navigate as there is no discernible pattern laying them out. Many caverns are connected to each other off of large branches of water, but others are well hidden in labyrinth-like twists and turns within the vast network. Many of the more seasoned Iwagakure shinobi were required to spend months in the caverns learning their layouts and experiencing life within them as a form of survival training and in the case of emergencies.
The caverns have multiple entrance ways from the surface if you know where to look, but many of them have been filled in with the rubble from the village's destruction far above. The caverns can still be accessed however through other various means, namely Doton style ninjutsu, and via the waterfalls of the Waterfall Cliffs if one were skilled enough to survive the descent from the falls into the caverns.
