At the beginning of the 5th century BC, perhaps during the city’s renovation by the tyrant Theron, there were interventions to strengthen the fortifications.
The main objective of this building phase was to increase secure conditions by strengthening the defences.
The most significant additions were made to Porta I, where an important tenaille was built to defend the weakest point of the hollow where it stood. In the same area, works to channel and collect water from the aquifers saved it the city walls surrounding the sacred area and the Temple of Demeter.
Porta V also underwent interventions to increase its security. Its dimensions were reduced considerably to ensure its defence in a more stable way, and it was fitted with robust pillars that would increase its monumental effect.
In the same period, in the Santuario delle Divinità Ctonie (Sanctuary of the Chthonic Deities), the beaten earth floor was replaced by an opus signinum floor.