The citadel of Ashdod-Yam, situated on the Ashdod shoreline, was built atop the ruins of the Byzantine city at the site (Azotus Paralius), now covered by sand dunes. The citadel was surveyed in 1970 by A. Kloner and A. Berman. In 1985 the area of the eastern gate of the citadel was excavated by Y. Porath and S. Pipano. Three seasons of excavation were conducted from 1997 to 1999 in the citadel on behalf of the Israel Antiquities Authority, under the direction of D. Nachlieli, Y. Masarawah, M. Ein-Gedi, and F. Sontag.
The 1997–1999 excavations extended over the entire area of the citadel. Ceramic finds indicate that it was constructed in the Umayyad period. The latest find discovered in the excavations dates to the Crusader period; hence, the citadel probably remained in use until then. As the loci uncovered in this excavation were disturbed, it was difficult to clearly assess the different phases of construction. It has a rectangular plan (60 by 40 m) with a central courtyard, and is built of well-dressed kurkar stones (0.4 by 0.2 m) bonded with lime mortar. The citadel’s wall (maximum width 2 m) is reinforced on the outside by piers constructed at fixed intervals of 3–4 m; it is preserved to a maximum height of 8 m. Eight towers are incorporated into the wall: four are corner towers, the two eastern or inland towers are square and the two western or seaside towers are round; and four are semicircular towers guarding the two gates. Vaulted rooms, largely collapsed, are built along the inside of the citadel wall.