The "Water Clock", so called by A. Marzullo precisely for the complexity of its hydraulic structures intended for the collection and conservation of water (well and tank) which can be observed on the surface and under the pavement of the courtyard of this building, is a discovery that is still unequalled in the Western Greek world: this unique monument has been the subject of numerous studies with many different theories advanced on its chronology and on its purpose.
The water clock was invented to keep track of time. Although no one is certain when or where the first water clock was made, the oldest known example is dated to 1500 BC, and is from the tomb of the Egyptian pharaoh Amenhotep I.
In the ancient world, there were two forms of water clocks: outflow and inflow. In an outflow water clock, the inside of a container was marked with lines of measurement. The container was filled with water, which was allowed to leak out at a steady pace. Observers were able to tell time by measuring the change in water level. An inflow water clock followed the same principle as an outflow one, i.e. the steady dripping of water. Unlike the latter, the former’s measurements were in a second container instead. Based on the amount of water that dripped from the first container, one was able to tell how much time had passed.
Around 325 BC, water clocks began to be used by the Greeks, who called this device the clepsydra (‘water thief’). One of the uses of the water clock in Greece, especially in Athens, was for the timing of speeches in law courts.
The so-called water clock in Paestum it was probably not a water clock, but it is certain that it had to do with water: there are canals, there is a cistern under the floor.
Right here a stele was found inscribed with the name of Chiron, the centaur also linked to medicine, healing and ancient wisdom.