Defense system of the Venice Lagoon, Maritime fortification network in Venice, Italy.

The defense system of the Venetian Lagoon comprises multiple forts, batteries, and octagonal structures positioned at strategic water entry points throughout the area. These facilities controlled the various channels and passages with cannon platforms located at different levels to provide comprehensive coverage.

In 1380, during the war with Genoa, Venice cleared the Poveglia borgo and built an octagonal artillery fortress in front of the island to block the route into the San Marco basin. In 1538 the fort of San Felice opened at Chioggia, followed in 1543 by Sant'Andrea at the Lido inlet, designed by Sanmicheli. New octagons guarded the Malamocco inlet from 1571, and San Nicolò followed in 1591.

Sant'Andrea Fort shows how Venetians combined military engineering with their own architectural style, using limestone arcades and trapezoidal forms that blend defense with local design traditions.

Many of the fortifications are best viewed from the water, so boat tours are a good way to observe the entire system. Some forts like Sant'Andrea can be visited on foot, though accessibility varies depending on season and water levels.

The Maximilian Tower on Sant'Erasmo Island features a circular design with a rotating cannon platform that provided 360-degree coverage of the lagoon. This rotating construction was a technical innovation allowing the fortress to quickly respond to threats from any direction.