The cathedral has been on the UNESCO World Cultural Heritage list since 1985, together with the nearby St. Michael's Church because of its unique art and outstanding Romanesque architecture.

After renovations and extensions in the 11th, 12th and 14th centuries, the cathedral was completely destroyed during an air raid on 22 March 1945 and rebuilt from 1950 to 1960.

Some of the cathedral's treasures have been shown further afield, including at an exhibition at New York's Metropolitan Museum of Art.

After the establishment of the Diocese of Hildesheim in 815 by Louis the Pious,[2] a Chapel of St. Mary was built on the locations of the modern apse.

[3] Bishop Gunthar of Hildesheim, who was in office from 815 to 834,[3] had a small basilica with two round towers built immediately to the south of the chapel, which he dedicated to Saint Cecilia.

[4] The cathedral was built in 872 under Bishop Altfrid as a cruciform three-aisled basilica with a two-story westwork.

[2] It is an example of Ottonian architecture, with alternating column support and semi circular apses completing the naves.

His successor, Hezilo of Hildesheim, abandoned this plan and instead built on the old foundations, incorporating the surviving walls into the new building.

Further important renovations occurred up to the end of the fourteenth century but did not deviate from the ground plan of Bishop Altfrid's basilica.

[6] During the aerial bombardment of Hildesheim by the RAF and RCAF in World War II, the main building was almost entirely destroyed; only the westwork and the outer walls survived.

[2] Of the ancillary buildings, only the Gothic Anne's chapel (Annenkapelle), erected in 1321 in the middle of the cathedral's courtyard,[2] was mostly undamaged.

It was the only cathedral in Germany that had to be newly consecrated after its reconstruction, on 27 March 1960 by Bishop Heinrich Maria Janssen.

The baroque elements were abandoned in favour of a form which took its cue from the early Romanesque style.

[3] The most visible aspect of this on the exterior was that upper stories, and side towers added to the westwork in 1840, were not restored.

The roofs of the nave, transept, and cloisters were cast in concrete and covered with wooden boards on the inside to recall the appearance of ceiling beams.

[8] The reconsecration took until 1960 to complete because of various problems, chiefly the "Hildesheim Cathedral construction dispute" (Hildesheimer Dombaustreit), an argument between the Diocese of Hildesheim and the Land of Lower Saxony about the cost of the reconstruction and particularly about whether Lower Saxony was one of the legal successors of the Free State of Prussia which had undertaken to cover the cathedral's building expenses in 1803 (when it was still the Kingdom of Prussia) during the process of German mediatization.

During the reconstruction, the basilica of St. Godehard served as the bishop's church (cathedra), as it had in the postwar years.

The solemn reopening of the cathedral was on 15 August 2014, coinciding with the beginning of the Diocese's 1200 year jubilee.

[10] According to the story, Emperor Louis the Pious had to hold a Mass while out hunting in the middle of the forest.

The Emperor considered this a sign that the new bishopric should be established here (not in Elze as he had planned) and he should dedicate it to St. Mary, whose symbol is the rose.

It was thought that the end of the famous rose had come, but the roots were largely intact, and in the spring of 1945 it put out 25 new shoots.

[3] (The column was originally in St Michael's, where Bernward was buried, and has been moved there again during the restoration of the cathedral, possibly to stay.

[18] Other treasures include:[3] During the 2010–2014 renovations, many religious items from the cathedral were displayed at the Metropolitan Museum of Art in New York City, until 5 January 2014.

[24] The new cathedral bells will be named after witnesses of the faith, who enjoy particular veneration in the Diocese of Hildesheim.

Hildesheim Cathedral was declared a World Heritage Site by UNESCO in 1985, along with St. Michael's Church.

He added, regarding the situation in Syria: "Während wir hier einen Dom wiedereröffnen, brennen dort die Kirchen."