The historical importance of Ilsenburg Abbey goes well beyond its immediate surroundings:
The former Benedictine Abbey at Ilsenburg was founded during the years following 1003, replacing a former Royal Hunting Palatinate.
The second Romanesque Abbey church was built between 1078 and 1087 in Ilsenburg. It was the first German Benedictine church to have a triple nave at the east end and other reform characteristics which were then taken over by the so-called Hirsau churches – i.e. before the famous monastery church of Ss Peter & Paul was built in Hirsau between 1082 and 1091.
The partially preserved, patterned plaster floor in the abbey church represents one of the few precious objects of this size on European soil to date from the 12th century.
According to Hallinger the Ilsenburg Abbey reform of the 11th century represents a reform movement within the Benedictine Order, which became established partly independently of the Cluny reform. Although recent research shows that this claim has to be seen in relative terms, it is still justified to speak of an Ilsenburg reform (so-called Herrand reform after Abbot Herrand).
The Ilsenburg Abbey library was once one of the most significant in the Harz region. A few works from the abbey scriptorium have survived. Recent research shows that the original of the famous illuminated manuscripts of the Sachsenspiegel [a comprehensive book of law from the 13th century] is most likely to have originated here.
At present there are separate research programmes on Ilsenburg as Benedictine reform building (2), the plaster floor (3), the Herrand reform (4), and the library (5).