from amphorae of Dressel Type I, suggesting a construction date during the 2nd or 1st centuries BC. The concrete masonry piers provide the earliest evidence for the use of tufo and pozzolana concrete in water, probably dating to the late 2nd or early 1st century BC. Tufo and pozzolana are resistant to deterioration in basic solutions such as salt water, and therefore this type of concrete was used throughout the entire complex in structures that were in constant contact with water. There is also a continuous foundation of stone (only visible underwater) for a breakwater which offered protection on the southern exposure, as well as a series of discontinuous extensions of the breakwater protecting the harbor from the south and southwest winds; "their spacing suggests that they were constructed with the primary purpose of breaking the crushing force of the seas without affecting the flow of currents in and out of the enclosed harbor area." Fishery Excavations have uncovered the earliest known commercial fishery about 250 meters behind the port, complete with two long fish tanks and a fresh water spring enclosed in a Spring House (on the western embankment). According to McCann, "connecting channels allowed for a continuing circulation of water and fish as well as salinity and temperature control." The evidence points to a large-scale fishing industry at Cosa, and it is believed that there may have been a factory close by for salting fish and producing the fish sauce garum (trade in garum is thought to have been much more lucrative than most wines). Significance McCann points out that "the layer of mud deposited around and on top of the dock as well as the presence of many joining sherds suggests the possibility of destruction by a sudden disaster, such as a tsunami which swept into the inner lagoon." Today the port of Cosa is deserted and the inner lagoon is silted up; however this once-flourishing port provides valuable insights about Roman harbor construction and trade. It forms an important link between the natural breakwaters on the Greek and Etruscan ports and the elaborate engineering of man-made harbors of the Roman Empire (such as the Trajanic port at Ostia). The city was likely founded in order to provide a strategically defendable port "close to the sources of timber and supplies from the Tuscan hinterland which would be necessary in the creation of the fleets Rome soon was