Watch Free Online HD Moviesjoy. Just off the southern coast of mainland Greece lies the oldest submerged city in the world. It thrived for 2,000 years during the time that saw the birth of western civilisation. An international team of experts is using cutting-edge technology to prise age-old secrets from the complex of streets and stone buildings that lie less than five metres below the surface of the ocean. State-of-the-art CGI helps to raise the city from the seabed, revealing for the first time in 3,500 years how Pavlopetri would once have looked and operated.