Already 9 years ago, I went to West – Peloponese for my internship. At that time, I had never even heard of the Peloponese. But when I arrived I was impressed. The mass tourism that you may know of some places in Greece, wasn't (and still isn't) on the Peloponse.
The summer that I lived there, I visited Olympia. Olympia is probably the most known sight of interest. Not only did the Olympic Games started there, but there is still a lot to see. Every 4 years the Olympic flame gets lighted on in Olympia.
You can visited Olympia for only 6 euro's per person. When you visit Olympia, just buy a cheap combi ticket for the archaeological site and the archaeological museum for only 9 euro's per person.
Directly outside the archaelogical site is a great restaurant situated, Ambrosia Garden. It has a great garden and amazing Greek food.
Check out the trips that Authentic Greece organizes to the Peloponese! It's definitely worth it to visit.