Gerak (faclon) or Geronthrai Castle.
With the fall of Constantinople in 1204 the area around this fortification became Frankish territory and was known as the Principality of Achaea with Geraki being one of the baronies. In 1209 the French Knight Guy de Nivelet was granted this barony and built the castle. It is estimated the castle was completed about 1250.
By 1262 the Byzantines had taken control of the fortification after the defeat of the Franks at the Battle of Pelagonia in 1259. The Byzantines maintained control until 1460 when it was captured by the Turks.
The Byzantines were there for 200 years. In this period, it became one of the main medieval cities of Peloponnese. In 1460, Geraki was captured by the under Mohamed II the Conqueror. In 1463 the Venetians briefly occupied Geraki until 1468 when it was returned to the Turks.
Just 3 years later, in 1463, The Venetians occupied Geraki but left in 1468 and the Turks came back. Some time about 1700 the fortification was abandoned by the Turks and allowed to fall into ruin.