On the eastern side of the Piazza dei Signiori (today Kallergon Square) stands the three-aisled timber-roofed basilica of St Mark, which served the liturgical needs of the Duke and Venetian officials and functioned as their burial place. The original building, erected in 1239, was reconstructed after the earthquake of 1303/4 and repaired on several occasions thereafter. Its bell tower on the south side — known during the siege as the “Alarm Bell” — was partly demolished when the church was converted into a mosque.

Following the liberation, the building housed the “Minoa” cinema, and during the German occupation it was used as a grain store. Its restoration to its present form was carried out by the Society of Cretan Historical Studies in 1956. Columns of grey-green granite, set on high bases adorned with plaster acanthus decoration, and simple capitals support the clerestory, which is pierced by pointed windows. The elevated sanctuary terminates to the east in a straight wall. Of the six columns of the open portico, only two are original, and of their capitals only the southernmost survives.