Theodosius I

Theodosius I (lived 11 January 347—17 January 395 AD, reigned 19 January 379—17 January 395 AD) was the last emperor to rule the entire Roman empire before it was split between the West and East. He was a devout Christian and opponent of Arianism, an early heresy in the church. He convened the First Council of Constantinople in 381, determining that Arianism was heresy. He also engaged in many construction works in Constantinople (today’s Istanbul), including expanding the Forum Tauri, which became the largest public square in antiquity. Some of the remains of the forum can still be visited and seen in Istanbul.