The Vault of Knowledge is a repository of all Molenoid history and information, including the "Mapa Mundi", the famed Molenoid map of everything that consists of every cavern, tunnel, bridge, shortcut and hidey hole in Slugterra, and the missing chapter of the Book of Molemound found by Trixie.
At the entrance, it states the Molenoid's motto: "Ignorance is bliss". Inside the Vault of Knowledge, it is a dark maze that is difficult to navigate, which is the reason why the Molenoids choose ignorance over wisdom. Upon reaching the entrance to the Molenoid library, the door is sealed by Smolten and is unlocked by Eli using Torch, his Forgesmelter.
The building and all of its information are eventually destroyed by El Diablos Nacho using his Greneater. The Shane Gang manages to get hold of the "Mapa Mundi", and under Pronto's approval, Burpy burns the map so that Dr. Blakk won't go after its dangerous secrets, like the way to The Deep Caverns and The Drop.
- Keys to the Kingdom (First appearance)
- It is unknown how do Kord and Nacho are able to get in and out of the Molenoid library as the door is too small for their size.
- The famed Molenoid map of everything is called "Mapa Mundi", which means "Map of the World".
- "Mapa" is "map" while "Mundi" is "world" in Latin.