The Edict of Serdica proclaims the idea of religious toleration

"On 30 April 311, Roman Emperor Galerius issued an edict aimed to terminate centuries long persecution of Christians. He did so in Serdica (the forerunner of the City of Sofia). This was a remarkable civilization act, a unique document formulating for the first time the idea of religious toleration. Its content has been fully preserved in both Greek and Latin. Its release has been acknowledged as a turning point that created the background of making Christian faith official in Europe and across the world."