Here we'll look briefly into the archetecture of Byzantine Churches so you'll have an idea how they evolved. Many are dedicated to a particular Saint and people frequent each depending on what they are praying for and the Saints attributes. (Much as they worshiped the pagan gods)
Early Christian era churches are built in Basilica form. A long rectangle divided by 2 or 4 rows of columns into 3 to 5 naves (kleti).
The side columns support a second story, the tribune, usually intended, back then, for the ladies to sit in.
A domed cupola (trollos thollos) or the tower section, was added to the designs a little later and side extensions gave the structures the form of a cross. In the 11th and 12th centuries most churches were cruciform with a cupola.
Kapnikerea in/on Ermou St., in downtown Athens, is a good example of this style.The church generally has 3 parts: the narthex or great closed vestibule, the larger nave usually communicating by 3 doors with the narthex and lastly the sanctuary which includes the prothesis, the central apsis where the Holy Table stands and the diakonikon. The sanctuary is seperated from the nave by a marble enclosure, the iconostasion is formed with small pillars and usually holds that churches particular Saints Holy icon. Fine bas-reliefs fitted on to plates of stone are usually fitted between the pillars. Byzantine churches outside walls are of fitted stones surrounded by brick work and lets you know immediately its nature.