A labyrinth is a complex series of passages connecting each math within a concent to the next higher, e.g. Unarian to Decenarian or Decenarian to Centenarian. In the Concent of Saunt Edhar, there is no labyrinth connecting the Millenarian math to the others. Between Aperts, the labyrinths serve as the only way for an avout to graduate from one level to the next. The labyrinths are also a way to pass materials between maths.
During Apert, Fraa Erasmas navigates the labyrinth between the Decenarian and Unarian maths. It takes him about an hour and a half.
Suur Tulia joined the Decenarian math of the Concent of Saunt Edhar by walking the 'Labyrinth before Fraa Erasmas was Collected.