A step before Venice: landscape reconstruction at Altinum

Strategically located on the inner margin of the Lagoon of Venice, Altinum was one of the most important cities in the northern Adriatic since the Iron Age to Roman times. The origins of Venice are linked to the migration of the inhabitants, who abandoned the city in the 5th-7th century AD, seeking refuge from Barbarians in the nearby islands. The reconstruction of the ancient landscapes of Altinum is crucial for the definition of modes and timing of the colonization of the lagoon, which finally led to the foundation of Venice around the 9th century AD. Several investigations have been carried out with the collaboration of the Archaeological Superintendency and the support of ARCUS s.p.a. and Regione Veneto. Remote sensing has allowed for a detailed mapping of the city walls, street network, dwellings, public and religious buildings of Roman Altinum. The city stood on a 3.5 m high, 1 km2 wide mound, surrounded by a complex network of rivers and canals. Two large canals, detected with LiDAR, used to cross the urban center, providing direct connection to the lagoon. The harbour was located at the eastern outskirts of the city. Twenty-five corings were carried out in the city and in the harbour to maximum depth of 8 m. The mound consists of superimposed archaeological layers from Protohystory to late Antiquity. The city canals and the harbour basin are filled by 2-5 m of organic-rich clayey silt with abundant plant macro remains and lagoonal shells. The biological proxies of salt/brackish water vary in the core, suggesting fluctuations in the hydrological conditions; expected sea levels are -1 m asl. at 3000 BP and few decimeters below present in the Roman age. Pollen indicates phases of deforestation; the great diversity of herbaceous plants suggests a variety of human activities in the area (agriculture, farming, gardening) since the beginning of the common era. Some unusual plant remains possibly document trades.