The erection of the basilica was ordered by Archbishop Gero in 1015, and it was long considered Magdeburg’s most venerable sacral building after the Cathedral. Custom had it that the mortal remains of Magdeburg's bishops were laid out here on the first day of their death before they were transferred to the Monastery of Our Lady on the second day and finally buried in the Cathedral.
Every year on 20th January, St. Sebastian’s head reliquary was carried in procession from the Cathedral to St. Sebastian Church. Public opinion in Magdeburg had it that this reliquary miraculously protected the city from an invasion of Henry IV's troops in 1075, and therefore it was highly revered by the citizens. After a fire the Romanesque basilica was transformed into a Gothic hall church in the 14th and 15th century. Today you can still admire the original outline, the towers and the transept in Romanesque style as well as marvel at the many valuable exhibits form the Middle Ages and modern times.