The Hellenistic and Roman walls of Nicaea have disappeared, with only traces of triumphal arches of Vespasian and Hadrian which were incorporated into the city gates. The earliest phase of these walls were begun Gallienus (253-268) and completed Claudius Gothius (267-270) when the region was threatened by the Goths. These walls formed an irregular pentagon around 5 km long. The original wall was single, perhaps with a ditch. The semicircular towers were about 60-70 meters apart. Twin towers flanked the gates. The walls were damaged during the Arab siege in 727, requiring substantial repairs. The walls west of the Constantinople Gate were completely rebuilt, during which time the inscription of Leo III (716-741) and his Constantine are recorded as builders, executed by curopalates Artavasdos. Michael III (842-868) made additions to the walls, in connection to a major program of defense in Asia Minor. This involved added new towers between the old towers on the southeast and east walls. Rebel Bardas Skleros besieged the city in 978, destroying a tower near the south gate. Alexios Komnenos erected a small bastion, which was faced with spolia from a Seljuk cemetery.  The wall was damaged in the earthquake in 1065, thus requiring extensive repairs. Extensive work took place under the Laskarids when Nicaea was the capital of the empire. In particular, two great corner towers were built on the southern wall. John Vatatzes added an outer wall with towers.