Argos is the main city in the Argolid, an area of the northeastern Peloponnese divided into two distinct regions: a rich central plain and a mountainous perimeter. The ecclesiastical and secular remains in the region dating to Late Antiquity suggest that it may have had its own school of mosaicists. After devastation by invasions in the late 6th and 7th centuries, the Argolid was partially settled by Slavs, but the Byzantines regained control of the area by the 9th century. The first attested bishop of Argos participated in the "Robber" Council of Ephesus in 449. By the l0th century Argos was combined with Nauplia as a bishopric. In 1188/9 Isaac II promoted the See of Nauplia and Argos to the status of metropolis.
In the 12th century the Argolid was particularly wealthy, if the number of surviving churches is any measure. They are found not only in the plain, at Argos, Chonika, Merbaka, Areia, and elsewhere, but also in the mountainous east at Ligourio and Damalas. Most of these churches display a similarity of style that suggests a local school of architecture. In the late 12th century powerful land-owners came to the fore, the most important of whom was Leo Sgouros. Before the fall of Constantinople in 1204, Leo Sgouros had already been planning to build up a principality in Greece. He had occupied Argos and then Corinth, with its impregnable citadel of Acrocorinth – where he died in 1208. After 1205 the Argolid fell under the control of the duke of Athens, and Frankish forts were built (or rebuilt) at the Larissa of Argos and Nauplia, which important in conflicts of the era. The Venetians came to dominate the east coast, purchasing Argos and Nauplia in 1388. Yet Theodore I Palaeologus, the Despot of Morea, captured them before they could claim them. The Venetians did manage to capture Nauplia, but were unable to capture Argos from Theodore. In 1394 Theodore signed a treaty with Venice, relinquishing Argos. In 1462, Argos finally fell to the Ottomans.
The Church of the Dormition of the Virgin
This church at Merbaka (now Agia Triada) is a domed, cross-in-square church of the composite four-column type, with a narthex and porches. The wall masonry is pseudo-isodomic in the lower section and "cloisonne" in the upper part. The facades are decorated with a variety of brick ornaments. The church was built on a stone crepis and dates to the end of the 12th or the 13th century. The interior is decorated with Byzantine wall paintings.
There is no reference to the history of the monument, which is dated only on the basis of the excavation data and its architectural form. It was probably connected with the antiquarian archbishop of Corinth, William de Meerbeke. Excavations carried out in 1989 and 1990 have brought to light the crypt under the sanctuary of the church, the stylobate of the the original iconostasis, and the graves inside the naos and the narthex, dated to the Late Byzantine or Ottoman period.
Oxford Dictionary of Byzantium
The Lost Capital of Byzantium: The History of Mistra and the Peloponnese by Steven Runciman
Argolis (Religious Greece)