After the death of the Arian Emperor Valens, the synod of Antioch in 379 asked Gregory to help resurrect Constantinople to Nicene orthodoxy. While the most important churches were still headed by Arian bishops, Gregory transformed his cousin's villa into the Anastasia chapel. From this little chapel he delivered five powerful discourses on Nicene doctrine, explaining the nature of the Trinity and the unity of the Godhead. These are called the "Theological Orations." By the time he left Constantinople two years later, there did not remain one Arian church in all of the city.