During the transitional period (7th-8th century AD), both in Greece and in the eastern regions of the empire, the repair and completion of earlier fortifications can be observed, with the common feature of reusing older building materials, after the extensive destruction caused by the severe seismic events of the 7th and 8th centuries and the intensification of enemy raids.

The appearance of the Arab threat in the Aegean from 649 AD and the gradual loss of the Byzantine provinces that supplied the capital and the Byzantine army with raw materials highlighted the strategic position of Crete as a source of supply for the capital and the need to protect the trade routes that linked it to Constantinople. In this context, from the middle of the 7th century and throughout the 8th century, attempts were made to reorganise the island’s administration and its defences by rebuilding the older fortifications or constructing new ones.

In this context, the reconstruction of the Hellenistic fortifications of Herakleion after the middle of the 7th century, as documented by the excavations at Bentenaki, was crucial for the protection of the city and its harbour. The construction of the Early Byzantine period is clearly distinguishable from the previous one: the inner core consists of rubble masonry and the outer face of dressed limestone from the Hellenistic period, which has been cut and properly assembled. A rich mortar of lime, pebbles and kurasan was used as a binding material, and scattered fragments of brick filled the joints. The same construction technique can be seen in several fortifications of the same period throughout the island, such as those at Gortyn, Kydonia (Chania) and Eleftherna.

The fortification, built on the remains of the Hellenistic enceinte, followed its course, surrounding the city and the port, reaching at least as far as Chandakos str. to the west, Daidalou str. to the south and Beaufort str. to the east. Its remains are preserved in various places, embedded in the Venetian fortifications. The southern and south-western sides may have been surrounded by a moat from the beginning, as was the case in Kydonia. The existence of the moat is reflected in the name given to the city by the Arabs, probably before they conquered it: Rabd el Khandaq, the fortress of the moat.