There has been evidence of a precious church treasure at Cologne Cathedral since the 9th century. Initially kept in the “Golden Chamber” mentioned as early as 1212 and temporarily displayed to the public, the cathedral treasure was first exhibited in a museum setting in the mid-19th century in rooms in the northern transept. Since 2000, it has been on display in the expanded 13th-century underground vaulted rooms on the north side of the cathedral.
Covering an exhibition area of approximately 500 square meters, spread over six exhibition rooms, visitors can view precious reliquaries, liturgical objects and vestments, as well as the insignia of archbishops and cathedral clergy from the 4th to the 20th century, medieval sculptures, and Franconian grave finds
The two-story medieval sacristy cellar displays various bishop's croziers belonging to archbishops and auxiliary bishops, processional crosses, chalices, monstrances, and other liturgical objects and textiles, while the reliquary chamber houses the cathedral's most important relics. The other rooms are dedicated to the worship of the Three Kings, early medieval Frankish graves, and medieval sculptures from the cathedral. The so-called library temporarily displays manuscripts from the cathedral library as well as special exhibitions on various topics. The historic vaulted rooms with remains of the Roman city wall, columns from the cathedral's predecessor building, and modern architecture, together with the presentation of the cathedral treasure, allow visitors to experience the eventful history of Cologne Cathedral in an impressive way.