Re-built during the late 1500s, the Library of Isotheos stands at the centre of Katadesis. During the 1800s, the vast collection that had amassed separated into the disciplines of economics, world history, the arts, engineering and the sciences.. Taking forty years to complete, it housed each within its own library. The original library is used for meetings of the council and ceremonial events. Although certain ancient manuscripts remained within its walls.

The name Isotheos comes from ancient Greek, meaning one who is separated from the ordinary ‘equal to the gods.’ It is thought this refers to the pursuit and acquisition of knowledge. Although interpretations differ with some believing the reference to be more literal. The original library is said to have been built after the fall of the library of Alexandria two thousand years ago with many of the manuscripts it holds dating back much further.