Final answer:
Proximity to a seaport was crucial for Roman trade due to the cost-effectiveness of sea shipping compared to overland routes, enhanced trade facilitation, and reduced risks of taxes and banditry.
Step-by-step explanation:
Proximity to a seaport was of utmost importance to Roman trade because shipping by sea was significantly less expensive than overland trade. For example, the bustling seaports on the Italian peninsula facilitated trade across the Mediterranean, making cities like Rome prosper. In contrast, inland city-states that had no access to seas, such as those in the Po valley, were limited to overland trading routes which were more costly and slower. Goods had to pass through various territories, incurring taxes, and were at risk from bandits.
Hence, maritime cities like Venice thrived by capitalizing on trade routes that connected Europe to the East, including the lucrative trade in spices, silks, and other precious goods from the Levant, which were highly desired in Europe and contributed to the growth of wealthy trade hubs along the Italian coast.