The crypt of Saint Philothei is a small natural cave which was turned into a small church by the daughter of a well-known Athenian family of the time, Rigoula Benizelou in order to pray. Rigoula Benizelou lived in the 16th century, during the years of the Turkish occupation, and after her martyrdom, the church honored her as a saint with the name Saint Philothei.
The crypt was accidentally discovered in 1934 during quarrying. It slowly took its current form while it has been established that it communicated, through an underground tunnel, with the metochi of Kalogreza that she had founded on her family estate. The discovery of the crypt became an occasion to rename the settlement of Nea Alexandria, as it was then called, to Filothei.