[3][4] After the downfall of the Western Roman Empire, Torcello was one of the first lagoon islands to be successively populated by those Veneti who fled the terra ferma (mainland) to take shelter from the recurring barbarian invasions, especially after Attila the Hun had destroyed the city of Altinum and all of the surrounding settlements in 452.

[5] Although the hard-fought Veneto region formally belonged to the Byzantine Exarchate of Ravenna since the end of the Gothic War, it remained unsafe on account of frequent Gothic (Sarmatian) invasions and wars: during the following 200 years the Lombards and the Franks fuelled a permanent influx of sophisticated urban refugees to the island’s relative safety, including the Bishop of Altino himself.

[8] Thanks to the lagoon’s salt marshes, the salines became Torcello’s economic backbone and its harbour developed quickly into an important re-export market in the profitable east-west-trade, which was largely controlled by Byzantium during that period.

[11] A further serious issue for Torcello specifically was that the swamp area of the lagoon around the island increased by the 14th century, partly because of the lowering of the land level.

As a result, by the late 14th century, a substantial number of people left for the islands of Murano, Burano, or Rialto (modern-day Venice).

One small palazzo is the only remaining medieval structure, consisting of a cathedral, a church, the town's former council chamber and archives (which house the museum), and the nearby basilica and campanile; the latter two were rebuilt in the year 1008.