Peloponnese - History Tour and more
The best option to explore Peloponnese is to rent a car. You can drive from Athens using the highway E94.
The car will give you great flexibility in visiting the suggested places. Plan at least 4 days to do the grand Peloponnese tour (not including islands.)
If you like to take it slow and visit also some islands, you will need at least 1 week.
Keep in mind that the organized tours you might come across visiting Peloponnese, do not cover all the sites and places.
The ideal place to start your tour through Peloponnese, is the Corinth Canal.
The idea of constructing a canal through the Isthmus of Corinth dates back to ancient times. Various Greek rulers and Roman emperors attempted to build it, but it wasn't until the late 19th century that the modern canal we see today was completed. Its historical relevance and the engineering feats involved make it an intriguing site to explore.