The island parishes were separated from each other by marsh or water, but waterways had been established to connect them. There was already a pattern of habitation that grew steadily more intensive and determined. The drive towards cohesion was advanced by another invader. In 810 Pepin, the son of Charlemagne, brought his forces to the lagoon in order to claim it for the Frankish Empire. He attempted to storm the ducal seat of Malamocco, and the doge fled to the islands of the Rivoalto for protection. It is said that Pepin followed in pursuit, but that his fleet became enmired in the marshes and receding waters; that he despatched rafts made of timber and brushwood, but that Venetian sailors destroyed them; and that an old woman directed them across the treacherous shallows with the old Venetian instruction,
It prospered, too, from its secluded position. In a treaty of 814, it was agreed that Venice would remain a province under Byzantine rule but that it would also pay an annual tribute to the Frankish king whose seat was now in Italy. This may sound like a double obligation, but in fact it freed Venice from single domination. It now stood between Franks and Byzantines, between West and East, between Catholic and Orthodox; its central position allowed Venice to steer a somewhat uncertain course, sometimes leaning to one side and sometimes to the other. It also provoked many disagreements among the ruling families of the lagoon, which had different allegiances and loyalties among the parties of the mainland and of the Eastern Empire. Nevertheless the position of Venice effectively secured its independence. One of the clauses of the treaty of 814 allowed Venetian merchant ships to sail freely to and from Italian ports. The Venetians, in other words, were able to trade. They could move between East and West. Venice became, predominantly, a city of merchants.
And it grew very rapidly. Many of the inhabitants of the lagoon soon migrated to the small islands around the Rivoalto. By the end of the ninth century there were some thirty island parishes, and by the close of the millennium there were more than fifty; the effects of a fire in 976, when three hundred houses were destroyed, is a testimony to the dense population. Those parishes grouped closest to the Rivoalto became connected by bridges or canals. The ramparts were erected, the marshes drained, the dykes constructed; the swamps were reclaimed, and the ground made fertile. Some of the major streets, surviving still, were then first laid out as footpaths. Stages and landing stairs were built, some public and some private. Dams were created to prevent the silt from the rivers washing into the lagoon. A service of ferry boats was instituted. Venice became an urban mass, hot and energetic, fixed upon the mud and water. It represented a vast human and communal effort, urged on by necessity and practicality. The goal of common existence was always there. There was a desire to make or to reclaim land, to conquer the water, to unify and to protect the common soil.
Venice in the ninth and tenth centuries was a medieval city, where pigs roamed about the streets and where pastures and gardens interrupted the vista of houses and churches. There were districts with the epithet “In the Marsh” or “In the Wilderness” or “In the Seaweed.” The citizens travelled on horseback along the main street, the Merceria, and tethered their animals to the great elder trees which flourished in what is now the Piazza S. Marco or Saint Mark’s Square (otherwise simply known as the Piazza). There were flat wooden bridges, without steps, connecting the islands. There were trees along the banks of the canals. On the surrounding islands there were meadows where cattle and sheep grazed; there were vineyards and orchards; there were ponds and small lakes. On the central islands, which gradually coalesced, there were courtyards and narrow alleys that bequeathed to the