Mother Cathedral of Holy Etchmiadzin and Zvartnots Cathedral

Mother Cathedral of Holy Etchmiadzin
Mother Cathedral of Holy Etchmiadzin is a 4th century Armenian church  in the town of Ejmiatsin, Armenia.  It is also the central cathedral of theMother See of Holy Etchmiadzin of the Armenian Apostolic Church.
Etchmiadzin Cathedral is listed among the UNESCO World Heritage Sites.
The Etchmiadzin Cathedral is the oldest state-built church in the world. The original vaulted basilica was built in 301-303 by Saint Gregory the Illuminator  when Armenia became the first officially Christian country in the world. Gregory had converted King Tiridates III  and members of his court.
According to the 5th-century Armenian annals, St. Gregory had a vision of Christ descending from heaven and striking the earth with a golden hammer to show where the cathedral should be built. Hence, the patriarch gave the church and the city the new name of Echmiadzin, which may be translated as "the place where the Only Begotten descended".
In 480, Vahan Mamikonian,  the Sassanian governor (marzban) of Armenia, ordered the dilapidated basilica to be replaced with a new cruciform church.
In 618, the wooden dome was replaced with a stone one, resting on four massive pillars linked to exterior walls by arcades. This was the church much as it is today.
Murals in the interior and extravagant rotundas surmounting the apses appeared in the early 18th century. A three-tier belfry was constructed half a century earlier.
The cathedral formerly boasted the largest collection of Armenian medieval manuscripts, but these were lately handed over to the Matenadaran in Yerevan.

Zvartnots Cathedral
Zvartnots Cathedral (meaning "celestial angels") are the ruins of a seventh century centrally-planned aisled tetraconch  type Armenian cathedral built by order of the Catholicos Nerses the Builder from 641-653. It is located at the edge of the city of Etchmiadzin  in the Armavir Province.
Zvartnots was built at a time when much of Armenia was found under Byzantine control and during the early invasions of Armenia by the Muslim Arabs. Construction of the cathedral began in 642 under the guidance of Catholikos  Nerses III (nicknamed Shinogh orthe Builder), who built the majestic cathedral dedicated to St. Grigor at the place where a meeting between king Trdat III and Gregory the Illuminator  was supposed to have taken place. According to the medieval Armenian historian Movses Kaghankatvatsi the cathedral was consecrated in 653. From 653 to 659, Nerses was in Tayk  and the construction of the cathedral continued under Anastas Akarratsi. Following the Arab occupation of Dvin and the intensifying wars between the Byzantine and Arab armies on the former's eastern borders, Nerses transferred the patriarchal palace of the Catholicos from Dvin to Zvartnots.
Zvartnots remained standing up until the end of the tenth century; afterwards, historical sources are silent as to the cause of its collapse. A close imitation of the cathedral was carried out by Trdat the Architect under the reign of Gagik I Bagratuni during the final decade of the tenth century. The contemporary Armenian historian Stepanos Taronetsi referred to Zvartnots when describing the church that Gagik I had inaugurated as "a large structure at Vałaršapat [Vagharshapat], dedicated to the same saint, that had fallen into ruins."
Zvartnots remained buried until its remains were uncovered at the start of the 20th century. The site was excavated between 1901 and 1907 under the direction of vardapet Khachik Dadyan, uncovering the foundations of the cathedral as well as the remains of the Catholicos palace and a winery. The excavations furthermore revealed that Zvartnots stood on the remnants of structures that dated back to reign of the Urartian king Rusa II.