Around the bell tower of the church, venomous snakes appear and begin crawling everywhere in the church, and particularly around an icon of the Virgin Mary. The snakes remain in the area of the church until August 15th, the feast day of the Dormition of the Virgin Mary. As soon as the Liturgy concludes on the 15th of August, they disappear back into the wilderness of the area. The snakes are not seen again until the following year.
The chapel at Markopoulo is built on the ruins of a convent. The local legend varies but the general gist of the story that remains is this:
In the early 18th-century, the nuns of the convent there were attacked by pirates. After praying to the Virgin Mary for protection from the pirates, the nuns were transformed into snakes. When the pirates entered the convent they were terrified by the sight and fled.
Every year since then, snakes have mysteriously appeared during the days of early August, venerating the icons there, leaving after the feast itself.
The snakes have failed to appear twice: in 1940, the year Greece was brought into the Second World War, and 1953, the year of a devastating earthquake on Kefallonia. Because of this, it is believed to be ominous if the snakes do not appear, or appear.