Agionori is known for the Agionori Fortress, which still stands at the top of the hill and was once connected with the castles of Argos and Akrocorinthos. Close to the village, in a narrow passage of Kleisoura the homonymous battle took place in which Nikitaras, Papaflessas and Ypsilantis decimated the remnant of the Turkish troops of General Dramalis’ after the battle of Dervenakia. Findings in the area identify the first signs of habitation as far back as ancient times.