We use Tolo as a base for travelling around the Peloponnese. Our favourite places (in no particular order) are
Napflion
Kalavrita (and surrounding countryside) also Cave of Lakes on the way.
Ancient Corinth (included with a trip through the canal)
Monemvasia (the coastal drive from Tolo has some wonderful scenery)
Mystras
Mycenae
Olympia
Epidavros
Dimitsana
The shrine of Ag Theodora at Vastas (just south east of Megalopoli) on the E65 going towards Kalamata, then a turn to the right off this road.
When we hire a car we also include a trip from Galatas across to the island of Poros (which I know isn't on the Pelopennese but it is a nice drive through countryside.
And many more. I'm sure you will have a great time.
The shrine of Ag Theodora is amazing. It is a small building with several large trees (rumour has it that there are 30 trees) which grow on the roof and a river starts immediately under the building. The story is. Theodora dressed in mens clothes and went to fight in battle. She was fatally wounded and as she lay dying she said "Let my body become stone, my hair become trees and my blood become water" Hence the shrine. We have been twice and have been unable to find the roots of the trees.