At the centre of the southern side of the old fortifications, flanked by two quadrangular towers, stood the principal entrance, known in Byzantine times as the Castle Gate or Gate of the Forum, and in the early Venetian period as the Porta Maestra. Its original location was probably at the corner of today’s Daedalou str. and Martyrs of the 25th of August ave.

As the southern wall was thickened with the addition of the inclined bulwark during the 15^th c., the gate was transformed into a vaulted arcade and renamed the Portone. A wooden bridge, supported on corbels allowed passage across the moat.

Around the mid-16th century, a four-storey building was constructed above the gate to house storage and a prison (fondaco vecchio), giving the gate its imposing new form and the name Voltone. The upper section collapsed in the earthquake of 1856. The bulwark  between the towers is largely preserved below street level. The eastern tower, on which the London Hotel had once been built, was demolished between 1921 and 1929 to make way for the municipal building Achtarika, which housed the Scientific Society and the Vikelaia Library. The inner face of the tower’s southern sloping masonry is today visible in the building’s basement. The western tower was demolished in 1960.