The outer view of the church presents a square shape, but observing the ground plan one notices that it is rather round, with four semicircular corner conchs and one in the middle of the eastern side (where it is found the altar of the church), inscribed in a quadrangle. Two additional conchs, one at each side, of rectangular shape, are found at the middle of the northern and of the southern sides, forming a total of seven conchs, a feature to which the church owes its name. Originally, a concentric colonnade of eight columns of Ionian style, without flutings, ended up to arches that served to support the dome of the church. Today only three of them are preserved; the ones missing have been replaced by a wall. The entrance of the church is in the middle of the western side. One of the most interesting archaeological features is the masonry of the church, as much of the material used comes from ancient buildings: we can see a Hellenistic frieze with garlands with oxen’s heads, architraves, bases, pilaster- capitals and other architectural parts of the ancient temple, as well as mullions of the Early Christian period.
When built, in the 5th – 6th century, the church was a baptistery belonging to a basilica of the Early Christian period. The basilica had been partly excavated by Italian archaeologists, during the Italian domination of the island, but no trace of it has been preserved today. Recent restoration works in the interior of the monument have revealed interesting frescoes dated in the 12th or 13th century, presenting scenes of the life of St. John the Baptist, along with more recent ones dated in the 16th century.