Later, during the Middle Ages, the economy declined harshly, as agriculture and trade suffered due to war and between Greeks and barbarians. Great strides were made in improving agriculture after the discovery of iron, which was more durable than copper and could produce better agricultural tools to increase agricultural production which increased population growth. During the Archaic Age trade had a significant impact on the economy, especially in Corinth and Athens. Corinth experienced large amounts of sea and land trade due to its convenient geographic location which made it very accessible. Corinth was located on an isthmus that connected northern and southern Greece. Corinth experienced profitable trade and obtained large revenues from the pottery trade and port taxes. Corinth was also the main shipbuilding center of Greece during that period. Athens was also a bustling center for maritime trade and eventually became the leading exporter of ceramics