Ano Viannos during the Venetian era was the largest village in the province of Belvedere. It was therefore necessary for the Venetians to fortify the area very well. As we can see even today, there are some ruins of a Venetian tower found on the western part of the village, which was also used by the Turks. This tower was demolished during the Revolution of 1866.
South of Viannos, at Keratokambos area, there is a steep hill called Kerato (Horn). A warning tower was built there, ruins of which still survive today. Many such towers should have been built in the province of Viannos, which are however destroyed.