Reconstructed in the late 1500s, the Library of Isotheos serves as the heart of Katadesis. In the 1800s, its vast collection was reorganised into five fields—economics, world history, the arts, engineering, and the sciences—each housed in a dedicated library. The reorganisation spanned four decades. While the original library is now reserved for council meetings and ceremonial events, it still safeguards certain ancient manuscripts.

The name Isotheos derives from ancient Greek, meaning “equal to the gods,” a phrase often linked to the pursuit of knowledge. Interpretations, however, differ—some believe the reference is more literal. The original library was founded two thousand years ago, following the fall of the Library of Alexandria, and many of its manuscripts date back even further.