Two thousand years ago, (22-10 BC) on the windswept coast of the eastern Mediterranean, with Roman engineering and largesse, Herod the Great accomplished a remarkable feat by constructing a whole metropolis known as Caesarea, complete with palace, temple, hippodrome, theatre, paved streets, sewer, and water system. But just as remarkable--using formed pozzolana hydraulic concrete --Herod built at the foot of the city a colossal harbor, which would make Caesarea the maritime trading oasis of its day. In the study of this facility, this work will try to consistently discern and clarify between what is known, what is probable, what is likely and what is possible. Beginning with essential confirmation of archaeological discovery compared with historical record, a number of correlations and considerations will be brought into play to give a more accurate and complete reconstruction of the structure's overall appearance and function. Further as the title of this inquiry suggests, though Herod built the city and harbor, it was not without Rome's facilitation and Roman expertise. And though Herod promoted Caesarea's commercial concerns and therefore his own, Rome's interest in its own promotion in the eastern Mediterranean preceded Caesarea whose existence was mainly for the furthering of that purpose.