On a steep slope of mount Arakynthos, facing the lagoon of Aetoliko, is the cave of St. Nicholas. This is one of the most important cave monasteries of Greece with unique wall-paintings. Another small cave, with exceptional and rare frescoes is preserved about 20meters north of the main cave. Inside the cave there is a large stone temple which separates the cave sanctuary and nave, the center of which is preserved cistern which collected rainwater.

This great monastic center had, during the Byzantine era, a bibliographic codes copying workshop (scriptorium) and an equally rich library. Manuscripts from Saint Nicholas Kremastos survived in libraries of Western Europe. The iconographic program is unique. The two caves are decorated with exquisite frescos-paintings of the so-called Cappadocian art that reveal the connection of Aetolia and Acarnania in Cappadocia, Asia Minor and Constantinople. The frescoes date from the 10th to the 13th century.