One of the greatest natural resources is water. The human pursuit of clean drinking water dates back to ancient times. However, transporting it to cities, especially those located on flat plains, was a difficult task. To overcome this challenge, the Romans achieved one of their most grandiose feats of engineering: the aqueducts. These were among the most expensive public structures built during the Roman Empire.
Ancient Philippopolis was supplied with clean drinking water from the Rhodope Mountains. Two main water sources (captation points) have been discovered near the present-day villages of Kuklen and Markovo. Several aqueducts and one clay pipeline existed. Research indicates that Philippopolis first acquired an aqueduct at the end of the 2nd century and the beginning of the 3rd century AD, and during the 5th and 6th centuries they were renovated and improved. The path of one aqueduct has been traced as far as Roman Stadium Square, where a distribution reservoir (castellum) is believed to have been located to distribute water throughout the city. The best-preserved and most impressive aqueduct was built from bricks and stones and in some sections reaches a height of approximately 14 meters. The cruciform piers supporting the arched masonry water channel measure 3.40 × 4.40 meters. In its vertical structure, the aqueduct displays the typical Roman building technique of alternating rows of stone blocks and brick layers. This construction method is called opus mixtum, or mixed masonry. At regular intervals near the aqueduct's route, massive towers were built. These served for repairs, cleaning, ventilation, and regulation of the water system. A special production of building materials, primarily bricks, was organized for the construction, and these bricks still bear the stamps of the workshops that produced them.
Very few cities in Europe have preserved aqueducts. These were expensive and complex structures, affordable only to wealthy and important cities - another strong confirmation of the significance of Philippopolis in antiquity.