Later, during the Dark Ages, the economy declined harshly, due to the suffering of agriculture and trade due to war and between Greeks and barbarians. Great steps were taken to improve agriculture after the discovery of iron, which was more durable than copper and could produce better agricultural tools to increase agricultural production, leading to population growth. During the Archaic period, trade had a significant impact on the economy, particularly in Corinth and Athens. Corinth experienced numerous maritime and land exchanges due to its ideal geographical location which made it very accessible. Corinth was located on an isthmus connecting northern Greece and southern Greece. Corinth enjoyed profitable trade and obtained large revenues from its pottery trade and port taxes. Corinth was also the main shipbuilding center of Greece at this time. Athens was also a bustling center of maritime trade and eventually became the country's leading pottery exporter.