The small vaults of the narthex are decorated with frescos depicting the Ecumenical Councils of the Christian Church (Ecumenical = before the Great Schism of 1054, when the Churches of Rome and Constantinople parted). In Eastern Orthodox tradition there were seven of them: Nicaea I (325 AD), Constantinople I (381), Ephesus (431), Chalcedon (451), Constantinople II (553), Constantinople III (680) and Nicaea II (787).
On the arches in between: frescos with the representation of saints.

The frescos must be dated around the 12th century, since this part of the church was built in the mid-11th century, and the city of Myra was completely deserted by the early 14th century.

Correspondent: J.M.Criel, Antwerpen.
Source: Website of ‘stnicholascenter.org’ & Wikipedia.