Researchers have revealed how dramatic sea-level rise over 5,000 years transformed the coasts of northern Italy, Slovenia, and northern Croatia. This change profoundly influenced the lives of Mesolithic and Neolithic people, shaping the development of local communities. What was once land roamed by hunter-gatherers and later farmed by early agriculturalists is now submerged beneath the sea. The study, led by the University of Southampton in the UK and the National Institute of Oceanography and Applied Geophysics (OGS) in Italy, reconstructs the evolution of the region's landscape between 9,000 and 4,000 B.C. It shows that sea levels rose in stages, sometimes as much as 25 millimeters per year, gradually submerging plains and creating wetlands and lagoons. As the sea advanced inland, it reshaped the landscape, erasing previous formations and creating new ones, ultimately forming the coastal features seen today. The present-day Venice Lagoon, which is famous for its island city built on marshy ground, was once dry land located kilometers from the coast. The same goes for other towns in the eastern lagoons, such as Grado, and even modern coastal cities like Trieste, which would have once been situated on hills overlooking swamps and lagoons. The study's findings, published in the journal Quaternary Science Reviews, highlight the importance of understanding submerged landscapes in the study of prehistory, particularly in the northern Adriatic region. These underwater areas contain valuable information about how ancient people lived and interacted with their environment. Archaeologist Samuele Ongaro, lead author and Ph.D. researcher at the University of Southampton, explains that submerged landscapes are a critical but often overlooked part of prehistoric studies. By combining sediment core analyses with high-resolution geophysical data from OGS, the researchers reconstructed the lost landscapes, their environments, and their significance to prehistoric populations. The study identified key stages in the region's transformation, including a rapid sea-level rise around 8,400 B.C., which created tidal channels, marshes, and lagoons. Over the next 1,200 years, the sea rose by eight meters, repeatedly forming and submerging lagoons and marshes, pushing inland by kilometers. Another major rise of five meters after 6,000 B.C. shifted coastal features again, and by 5,800 B.C., the lagoons and landscape we see today began to take shape. The findings emphasize how Mesolithic hunter-gatherers had to adapt to a constantly changing environment, dealing with shifting habitats and resources like plants, fish, and game. The researchers hope future studies will uncover how these communities adjusted their activities in response to coastal flooding and how this influenced the eventual spread of farming in the region. Dr. Federica Donda, a marine geologist from OGS and co-author of the paper, notes that integrating geological and geophysical data allows for a better understanding of the environmental evolution of submerged areas. She highlights that the seabed is a crucial part of our archaeological heritage, as much of the land once inhabited by ancient people is now underwater. This research underscores the value of paleogeographic reconstructions in studying the development of past societies, offering a glimpse into a part of Europe's landscape that has been hidden for thousands of years.