During excavations at Bentenaki, a square tower of the older fortification was found in the backfill of the 16th century coastal fortification. The tower, which was converted into a church in the 14th century and demolished for the construction of the 16th century wall, had two construction phases. The lower phase, which has now been covered except for the upper row, consists of rows of large, dressed limestone without mortar. The “emplecton” construction system allows this phase to be dated to the Hellenistic period.  Above, the ancient building material was cut up and reused in a different way for the reconstruction of the fortification, which is dated by excavation evidence to the end of the Early Byzantine period (7th-8th century AD). The tower of Bentenaki rested on a wall that ran south-west towards Chandakos street.

The Hellenistic fortification of dressed limestone was first discovered in 1952 at the junction of Daidalou and Byzantiou streets. The ancient structure, which was preserved from one to seven rows high, ran along the base of a later rubble wall with rectangular towers, which was uncovered over a length of 28 metres, documenting that the later phase of the fortification, now considered early Byzantine, closely followed the course of the earlier one. Both the emplecton wall at the eastern end of Daidalou str. and the one discovered under the Astoria Hotel must be associated with the eastern course of the ancient fortification.

The Late Classical-Early Hellenistic layer on which the ancient wall of Daedalou str. was built should be regarded as the limit for dating the fortification. The fortification along Daedalus str. defined the southern boundary of the city during the Hellenistic period, outside of which only burials have been found. On the contrary, inside the fortification, in the area to the west and north of the Archaeological Museum, urban uses such as pottery deposits and workshops have been found.

The tower of Bentenaki and the part of the wall towards Chandakos str. are irrefutable evidence that the Hellenistic fortification reached the harbour and probably enclosed the coastal front, including the harbour and the moors, as was the case in other important Hellenistic ports of Crete (Falassarna, Hersonissos). This hypothesis is supported by the large number of dressed limestones of similar dimensions to those at Bentenaki at the base of the 16th century coastal fortification, from the 18 Anglon square to the bay of Dermatas, at the base of the Venetian fortress of Rocca a Mare (Kules), at the base of the windward moor and on the breakwater of the leeward moor, which was demolished together with the small Kules at the beginning of the 1930s. Finally, halved limestone was used on the western and northern faces of the Sabbionara bastion. The quantity of material confirms the size and length of the structure. On the basis of these data, the fortified Hellenistic city of Heraklion would have covered an area of about 270.000 m², i.e. a quarter of the area of Hellenistic Knossos.

The older but persistent view of the limited extent of the ancient city is based on the discovery of Roman tombs from the 3rd century AD along 25th Avgoustou avenue. Thus, the boundaries of the city were defined from Chandakos Street to 25th Avgoustou Avenue.  However, the location of the Roman tombs only suggests that the earlier fortification had been destroyed or fallen into disuse centuries after its construction, and that the western boundary of the city had shifted.