This latter, sometimes called Nazianzum, is a place quite unknown to early writers, and derives all its importance from its connection with our Saint.  The Romans seem to have called it Diocæsarea.  This would place it in the south-western portion of the district called Cappadocia Secunda, a sub-division of the Province, which had previously included the whole country of Cappadocia under the Prefect of Cæsarea.  The Emperor Valens made the division for financial purposes about a.d. 371, and assigned Tyana as its civil Metropolis, and, as we shall see, thereby caused an ecclesiastical quarrel which had considerable effect on the life of S. Gregory.  Tyana was situated at no great distance south and east of Nazianzus, which place is usually identified with some interesting ruins about eighteen miles south-east of Ak Serai, on a rocky platform at the foot of the mountains called Hassan Dagh.  Amongst other ruined buildings here are the remains of three Byzantine churches of great age, but more recent than the rest of the town.