St Gregory of Nazianus (St Gregory the Theologian, c.329-389) was one of the so-called Cappadocian Fathers whose writings and teachings helped establish some of the fundamental tenets of Christianity.
A close friend of St Basil of Caesarea (modern Kayseri), Gregory spent much of his life battling what were then seen as heresies but now look like so much theological nit-picking while living in what was then Gelveri and is now Güzelyurt.
He was briefly bishop of Constantinople (İstanbul) and it’s there, in the Greek Patriarchate in Fener, that some of his remains have eventually come to rest after Crusading shenanigans that saw them carried off to Rome in 1204.