In 1829, Gregorios Stephanos had funded the construction of this church which constitutes the Catholic parish of Ermoupoli. On an inset inscription in latin above the entrance the visitor can read the name of the owner, the date of the construction and the name of an architect, coming from Tinos island Hadjisimos (or "Χ' Σήμος" as it is written on the inscription). Because of the inclination of the ground, the church is built on a raised surface. This three-naved basilica follows some elements of the Italian style. The three naves are defined by two arched colonnades.
The particular style of the capitals of those columns can also be seen in other churches of Syros (Agios Gheorghios, Metamorfosi, Kimisi). As in the church of Metamorfosi, the central nave has a cylindrical vault and two groined vaults on each side, forming a cross shape.
Embedded lesenes are found on the walls forming the outer naves and over the central arcade. The motifs of the keystones are simple, some decorative bands and rosettes, painted with pale colours. Right in the center of the church, on the floor, you will see the commemorative plaque of Gregorios Stephanos, a great benefactor of Syros, who was buried in this church. On this plaque, offered by his nephews, one can see the engraved inscriptions that explose the exceptional position that this man held in the society of Syros and all the titles that had been attributed to him.