In Philippopolis the deviation angle of cardo maximus (the main North-South road) is 16 degrees to the West. This shift derived from the nature of the site with the three hills where the town was established. The geometric centre of the Ancient city of Philippopolis was the town square (Forum or Agora as these central urban spaces were called during the Roman Empire), where the two main streets of the city – cardo maximus and decumanus maximus, intersect. The streets parallel to them, when intersecting, form quarters, called insulae. In the area around the Forum - the Agora, the insulae were occupied by buildings with public functions: the Odeon, the Library, the Treasury.
Initially, in the 1st century AD, the pavement of the streets was of cobblestone and gravel and there was no drainage. Later on, at the beginning of the 2nd century AD, the reconstructions in the central urban zone of Philippopolis affected also the street system. The direction was kept the same but the pavement was replaced. Most of the streets in the Ancient city were paved with blocks of syenite of different sizes and geometric shapes. During that period the drainage of the city was also being developed. Both sides of the streets were limited by curbs. During this period, the sewerage system of the town was developed. Along the axis of the most streets (under the pavement) masonry canals for the wastewater were conducted.
