From Piraeus, drive down the modern highway past Eleusis until you reach the ancient town of Corinth where Saint Paul lived and preached for two years. In ancient times, Corinth was amongst the richest cities and this is quite evident by its remains. Excavations of the area are still continuing today and have brought to light the Agora (marketplace), temples, fountains, shops, porticoes, baths and various other monuments you'll see. Peruse the nearby Corinth Museum, housing an impressive collection of antiquities unearthed from nearby areas. Most of them, including superb mosaics, are Roman in origin.
The next site you'll visit is the famous Corinth Canal. Boarding a local boat from the village of Isthmia, you'll navigate the canal that is considered an engineering wonder. Carved into a massive rock, the 76 foot wide and 26 foot deep canal dramatically separates the Peloponnese from the rest of mainland Greece. Before taking the return journey to Piraeus, a unique photo opportunity can be had 200 feet above water, from the center of the bridge that spans its banks.