In the eastern walls of the initial city, Dyggve's urbs vetus, there was a large gate. It was first studied by F. Carrara in 1846, and then completely excavated by Bulić in 1906. Later, a water supply system was built over the gate leading to the southern parts of the city. Because of its monumentality, the door was given the picturesque name of Porta Caesarea.
Both the gate and the walls next to it are obviously old. Heinz Kähler believes that they could have been built at the beginning of the first century AD, ie in the last years of the reign of Augustus (died 14 AD). Then, in the time of Prefect P. K. Dolabelle, the construction of many major roads began, some of which started right from Salona and, among other things, led to the hinterland of Delmat. They were built by the army, as evidenced by numerous inscriptions on the monuments, which archaeologist F. Bulić jokingly commented: "Soldiers did not waste time in their camps as they do today in their tents across Europe, dealing only with weapons in preparation for the slaughter of mankind."