From the official guide on the premises:
The great cathedral ... referred to as both Zvartnots and St. Grigor Lusavorich by medieval historians, was built on the spot where it is said Grigor Lusavorich met King T’rdat, initiating the king´s conversion and leading to
adopting Christianity as the sate religion (the first nation to do so, in 301). Armenia
The name is attributed to a vision Grigor Lusavorich had when establishing the Armenian Church, and has been variously translated as “Vigilant Ones”, “Vigilant Forces”, “Archangels” and “Celestial Beings”. The name may as well derive from the pre-Christian word “Zvarnonk”, given to a spirit believed to raise the dead, though this is not proved.
Inspired by an interpretation of the Apocalypse that predicted the second coming of Christ when the seven main churches of Christianity came together, Zvartnots was built to be the “seventh seal of the seventh tier of God’s presence on earth” (Revelation 11:15-19 of the Holy Bible). One of the tallest churches on earth when it was built, Zvartnots was the most significant architectural development in the Byzantine world.
Its architecture had a direct impact on the dome of St. Sophia in Constaninople, which collapsed in 558. The master architect for Zvartnots is said to have been commissioned to design St. Sophia’s dome using the tubular arch system developed at Zvartnots.