The Nui Caves were a mysterious network of caverns that stretched far beneath Voya Nui. Their name literally means "Great Caves." Of note is the fact that they did not lead to the Chamber of Life, and thus were not explored in the story.
It is assumed they were destroyed when Voya Nui slammed into the Southern Continent.
| Fire Regions: Mt. Valmai • Lake of Lava • Chamber of Life • Lava Reservoirs|
Water Regions: The Cape of No Hope • Lagoon Entrance • Mahri Nui (Formerly) • Voya Nui Bay
Village Regions: Matoran Stronghold • Matoran Village • The Jungle Sanctuary • Canyon Fortress
Piraka Regions: Piraka Stronghold • The Chamber of Truth • Piraka Outpost
Ignika Chambers: Staircase to the Ignika • The Zone of Nightmares • The Chamber of Death • Umbra and Protodax's Chamber • Lava Chamber Gate
Other Regions: Ring of Ice • Cavern of Historical Records • Desert of Sorrows • The Green Belt
Lake of Protodermis • Nui Caves • Stone Cord (Destroyed)