In the specatular Vouraikos Gorge, the villages of upper and lower Zachlorou lie 12 km from Diakofto and are well known as a stop on the way to the Great Cave Monastery.
The monastery is one of the best known in Greece and is a seven story structure built across the mouth of the Chelmos Cave. It was destroyed by fire in 1934 and re-built.
Dedicated to the Assumption, the monastery was founded by 2 monks from Thessaloniki: Theodoros and Symeon on the spot where in 342 AD a shepardess of royal descent found a miraculous icon of the Virgin in the cave. The icon was made of wax and mastich and inlaid with canvas and attributed to St. Luke.
The Monastery once possesed many important manuscripts and relics but most have been lost to fires over the years. Today Byzantine Gospels and relics may be seen.
In the middle ages the Monastery enjoyed special privleges from the Venetians and the Turks and during the War of Independence was fortified, sucsessfully repeling all attackers.
A small path leads to the top of the cliff where the remains of a fort and cannon may be seen. There is a hostel open to visitors and the views are exceptional.