Set at the top of a rocky mountain above Ancient Corinth are the remains of the medieval fort of Acrocorinth which is rarely visited it seems. The large site, with amazing views, still has some impressive structures including imposing gateways and a Frankish Tower. When we visited in 2018 we could see the smoke from the devastating fires that claimed many lives near Athens.
There is free parking and a cafe near the entrance. There are disabled toilets here too which is laughable as the entrance to the site is up a steep and very slippery path, completely wheelchair and disabled unfriendly. Able bodied people struggled to stay on their feet by the main gate.
We were lucky, on the day we visited it was overcast and threatening storms, so the temperature was comfortable, on a hot day I can imagine it would be hard work. There is a box office and there should have been a charge for entry but on our visit no one was bothering.
Views from Acrocorinth. 
Smoke from the fires near Athens viewed from Acrocorinth.
Gruntie's Travels 