In order to fortify the weakest positions in the enceinte and keep the enemy even further from the ditch and the walls, the Venetians built twelve additional outworks to serve as heavy artillery emplacements.

Defenders reached the outworks by means of underground passages that ran from the ditch.

The only such defence still extant is the Fortress of St. Dimitrios, to the east of the enceinte opposite the Vitturi Bastion. All the other outworks have been demolished, though their trace survives in the outline of modern building blocks.

The Fortress of St. Dimitrios on a map by Giorgio Corner, 1625 (Giorgio Corner, Biblioteca Nazionale Marciana, Venice)
The surviving section of the Fortress of St. Dimitrios, 2004 (photograph: G. Papanikolaou, Yiorgos Papanikolaou)