[1] An expedition led by doctor and academician Rosen Milev was carried out on 18 January 2004, affirming that the monastery was founded by Athanasius of Alexandria in 344 while returning from the Council of Serdica in present-day Sofia.[2] On the way back he stopped and slept in a Roman fortress, the remains of which are located close to today's monastery, deciding to found a monastery due to the strong influence of the Arians (see Ulfilas), whom he considered heretical, on the Goths living in the region of Beroe[citation needed] (modern Stara Zagora).This is regarded to be proven by the passional of Saint Athanasius and the annals of the Patriarchate of Alexandria, as well as further research in the Vatican Secret Archives.[citation needed] The existence of the monastery during the Middle Ages is evidenced by archaeological material.It was also visited by Bulgarian revolutionary Vasil Levski during his trips throughout the country in the late 19th century.