Athens in antiquity as well today, included all the settlements in the wider Attica region. That is why its official name was “the Athens” (plural). Since prehistoric times, the city of Athens and the wider region of Attica did not contain many natural water sources so aquatic reserves were never adequate to meet the needs of residents, as these changed through time. The construction of aqueducts was part of a more organized effort to address the water needs of the Attica basin area since prehistoric times. In the ancient city, tens of small and large aqueducts were built to meet the city's needs for water. The hydraulic structures of Athens were mostly underground, for safety reasons. The water was channeled through aqueducts to fountains. Many aqueducts were built during the pre-Roman period and they were often works of leaders or other eminent citizens of ancient Athens. A key step in developing the city’s water infrastructure took place during the Roman occupation of Athens when the Hadrianic aqueduct and the Hadrianic reservoir were built. The project was a huge achievement for the time and was one of the longest tunnels worldwide during the Roman era Construction began in 125 AD and was completed in 140 AD. The Hadrianic aqueduct was underground with natural flow requiring a small and continuous slope along the aqueduct. Wells, communicating through the aqueduct, were placed at regular intervals.
The main branch of the aqueduct - the central part of the Hadrianic, consists of the main tunnel, approximately 20 Km long, which starts from the foot of Mount Parnitha in the present day Olympic Village and ends up in the reservoir of Lycabettus, exploiting the water sources of Parnitha, Penteli and the Kifissos River. Gravity collected water from the water sources in the main tunnel and there was also the contribution of smaller aqueducts along the route. The secondary branches are composed of many transverse, which were designed to increase the water discharge capacity of the main aqueduct.
The Hadrianic was a project of continuous multi source collecting groundwater along its path. It was constructed below the surface at a depth of 2.5 to 40 m depending on the upper aquifer of the Athens basin, which fed local wells, in order to collect groundwater from that aquifer, too. The Hadrianic stopped being maintained during the Ottoman occupation and returned into service after the liberation of the city until it was gradually abandoned after the construction of modern water resource projects.