Koroni castle is inhabited so open (and free) 24 hours. Inside however the nuns normally close the nunnery gate at 5; ask them to allow you to climb for a 360° surround view at sunset onto the octagon tower on the highest point of the old acropolis, which the St John monastery has been occupying for the past 100 years. And admire their delicious mandarins, clementines, and oranges! 🍊