L'épître 17/77 de Grigor Magistros: Une description de la cathédrale Sainte-Sophie de Constantinople? (Grigor Magistros's Letter 17/77: A Description of Hagia Sophia?)
In a letter written to his son-in-law for the feast of the Inauguration of the Church, Grigor Magistros recalls the Illuminator's vision of an angel commanding him to found a martyrium. That site, mentioned by Agathangelos, is not precisely known, and Magistros almost certainly never saw it. Arevshatyan therefore proposes that his description is modelled on a building he had seen: Hagia Sophia in Constantinople, then the principal church of the Christian world. She adds that a miniature in a Matenadaran manuscript containing Magistros's complete works shows him standing beside a magnificent church, possibly alluding to the poetic contest at Hagia Sophia in which the Armenian scholar bested an Arab poet by versifying the whole Bible.