The area of the present Clementino port was the old port of Tarquinia that in the 181 a.C., became a roman colony and took the name of Graviscae. The excavations  in progress from 1969 had brought out some sectors of the inhabited of the colony and an important emporic archaic sanctuary ( the original one  go back at the beginning of the VI century a.C., after there were various stage of the construction) dedicated to Hera, Afrodite and Demetra. Those discoveries have allowed to rebuild the history of the settling, born about at the 600 a.C., lived prosperously till the roman conquest (281 a.C.) and, after the neglect of a century, revived (as Pyrgi) with reduced dimensions, but always of the normal greatness of those roman marine castra (about m 300 of side). 
The colony was nearly completely destroyed during the gotic invasion of the 408 d.C., even thought it was preserved by bishops untill the VI century d.C.. In the Middle age, on the same point of the roman port,  rised the Corneto port, important port of call of the zone, supplanted then by Civitavecchia.