On 30 April 311, the Edict of Toleration was issued by the Roman emperor Galerius in Nicomedia, ending Rome’s persecution of Christians. A porphyry portrait of the emperor was discovered during excavations at Felix Romuliana, Serbia, in 1993.
The palace compound near Gamzigrad – associated with Galerius since the find – was investigated by the Romano-Germanic Commission of the DAI together with Serbian partners from 2004 to 2012. New documentation of the fortified complex was carried out, along with an investigation of the immediate vicinity of the palace and a survey of the surrounding land.
In 2007 the imperial palace compound, which was never built over in modern times and whose circuit walls survive to a height of 10 m, was inscribed on the UNESCO World Heritage list.