Italian city Venice is founded with the dedication of the first church, that of San Giacomo di Rialto on the islet of Rialto.

The refugees hammering wooden pilings into a malarial swamp were not building a temporary shelter. According to tradition, Venice was founded on March 25, 421, with the dedication of the Church of San Giacomo di Rialto on a cluster of muddy islands in a shallow lagoon at the head of the Adriatic Sea. The settlers were mainlanders fleeing successive waves of barbarian invasions, and they chose the lagoon precisely because no army could easily reach them there. The founding date is almost certainly legendary, assigned centuries later to give Venice a neat origin story. Archaeological evidence shows gradual settlement of the lagoon islands from the fifth and sixth centuries, as inhabitants of Roman cities like Aquileia and Padua fled Attila the Hun's armies in 452 and later the Lombard invasions of 568. The lagoon offered one decisive advantage: its shallow, shifting channels were impossible to navigate without local knowledge, creating a natural fortress that no land-based army could assault. The early Venetians built on what they had: fish, salt, and geography. Salt production and trade made the lagoon settlements prosperous enough to attract permanent populations. By the seventh century, Venice had elected its first doge and begun building the maritime commercial network that would eventually dominate Mediterranean trade. The city's unique construction, with buildings erected on millions of wooden pilings driven into the lagoon floor, created an urban environment unlike anything else in Europe. Venice became the wealthiest city in the Western world by the 15th century, commanding a maritime empire that stretched from the Adriatic to Cyprus. The city that began as a refugee camp in a swamp produced Marco Polo, Titian, Vivaldi, and a system of republican government that lasted 1,100 years, longer than any other republic in history.