Mornos Lake was created as a reservoir for the city of Athens, which is populated by about 3.1 million people, representing about 40% of the population of Greece. To create it, a simple earthen embankment was placed across the Mornos River in Central Greece at 38°31′37.1″N 22°07′14.7″E. Though of earth, the soil is very compact. Monitored by GPS, the dam has a low rate of deformation and is considered one of the more stable in Greece. The fact that the dam is located in a region of high seismicity causes some concern and results in a higher level of monitoring.
The Mornos aqueduct is the sole conduit of water extending the entire distance from the reservoir to the processing stations of north Attica. That distance is 110 kilometres (68 mi), which is not exactly straight, but curves generally to the south and is positioned to take best advantage of the terrain. Because of the mountains, an aqueduct of this magnitude was impossible to ancient engineers, who constructed many effective aqueducts marvelous for their times. some of which stand partially yet. What the moderns have that the ancients did not are the modern methods of tunneling. The aqueduct runs through 15 tunnels for a distance of 71 kilometres (44 mi). Due to modern tunneling machines and laser measurement devices no mountain is beyond the capability of the engineers.
The method of transport is still gravity feed, the cheapest and most reliable in case of disaster. There is no need now for arched aerial structures porting water across valleys. Modern conduits go underground through steel and concrete structures far below the valley. For example, the Mornos aqueduct crosses the Pleistos valley at Delphi, but none of it is observable to the visitor, as it is deep underground. It was thought more practical to place the tunnel below the karst imperfections near the surface, as their irregularities would place variable stresses on the structure, facilitating topical wear and tear and creating ruptures.