Background Petersberg Citadel is entwined with the history of Erfurt. The city was first mentioned in 742 in a letter from
St Boniface to
Pope Zachary, when the Catholic Diocese of Erfurt was established. It was part of the
Holy Roman Empire, and was brought into the
Diocese of Mainz in 755. The earliest archaeological find from the Middle Ages on Petersberg hill is a coin dating from c.850, from the time of
Lothair I, Holy Roman Emperor from 817 to 855. It was found in a grave, in the mouth of the deceased. The oldest surviving building in the citadel is the Peterskirche (St. Peters Church), which was part of the
Benedictine Monastery of St Peter and Paul, after which the hill, and subsequently the citadel, was named. The first recorded evidence of the monastery is from 1060, but it may have existed a considerable time before that. The original building burned down in 1080, but was rebuilt from 1103 to 1147 and St Peter's Church is from this second period. About 1625 the city council had the city wall at the Petersberg strengthened by building a large
hornwork and two
bastions. These are the bastions named Gabriel and Michael. During the
Thirty Years' War (1618–1648), Erfurt was occupied by Swedish forces from 1631. The Swedish king,
Gustav II Adolf, hoped to build a fortress on Petersberg hill, but he died in 1632 and the plans never came to fruition. However, the Swedes did strengthen the existing Bastion Gabriel in 1643. In 1664 the city and the surrounding area were conquered by the
Electorate of Mainz. On 1 June 1665 the foundation stone of Petersberg Citadel was laid. A plan that the Erfurt architect (c.1660–1663) had created for the Swedish king Gustav II Adolf served as a basic model for the citadel, and the work was substantially influenced by (c.1620–1701) the architect to the imperial court of Mainz. The second construction phase was from 1707 to 1728, under the direction of the architect
Maximilian von Welsch (1671–1745), who was made an
imperial knight with the title
Edler von Welsch for his services to architecture by
Charles VI, Holy Roman Emperor in 1714. Welsch put special emphasis on the reinforcement of the fortress and trench defenses. He stayed in Erfurt from 27 September to 14 October 1808, when he meet with Tsar
Alexander I of Russia for the
Congress of Erfurt. The two leaders visited Petersberg Citadel together during the Congress. He also went to Erfurt on 15 December 1812 on his return from Russia to France, and from 25 to 28 April 1813. On 21 April 1813 he had ordered that Petersberg Citadel should be strengthened and equipped so that it could support 2000 men under siege for six months. Both French troops and civilian residents of Erfurt were put to work on the project, with over 3000 civilians working on building the ditches that surround the external walls. The work was carried both day and night, used flaming torches to see by. Prior to
World War I there was a renewed interest in the strategic military location of Petersberg Citadel. New buildings, such as workshops, warehouses, barracks and a military detention centre were built between 1912 and 1914.
Post World War I The fortress remained an important garrison position until the end of the war in 1918. After World War I, as a result of the
Treaty of Versailles in 1919, there was a gradual abandonment of military facilities during the
Weimar Republic period. Petersberg was used for garden allotments and by the civil police, who had a detention centre, garages, workshops and stores on the site.
Nazi period (1933–1945) When the Nazis came to power in 1933, they again brought the citadel into military use. They built gun
casemates, and from 1935 divisional army units, reserve army units and the district army recruitment office were based there. Also from 1935, the Nazis used parts of the citadel as a prison for the internment of their political enemies, such as communists and trade unionists. They were kept in a police detention centre originally built to accommodate up to 60 prisoners, but at its peak 241 internees were crowded into the facility. Many of the internees were sent directly from Petersberg citadel to
concentration camps. Some were murdered by the Nazis at the citadel itself. The Nazis also had a military court at the citadel for dealing with people such as
deserters, which could pronounce death sentences on those being tried, and sometimes these people were immediately executed at the citadel. Today there is a memorial to those mistreated by the Nazis at the site. Some war damage was sustained, including the 12th century Leonhardskirche (St Leonard's Church) which was totally destroyed in an air raid. The church had been converted into an artillery store.
Post World War II At the end of World War II, Erfurt was liberated by American forces in April 1945, and handed over to the Soviet administration on 3 July 1945, as agreed at the
Yalta Conference, held in February 1945. In 1944 a transit camp for displaced people had been established in the Defense Barracks, and this continued operating under the occupying Soviet administration after the war. In 1949 the
Soviet Occupied Zone became the
German Democratic Republic (East Germany). From 1947 Peterberg Citadel was used mainly for civil purposes, with barracks being used by the civil police. From 1956 until 1963 the
East German Army (German:
Nationale Volksarmee) used the citadel and its barracks, but they then moved to new facilities on the outskirts of the city. After that the main users of site were the police, for storing equipment, and a garden allotment association. The
Stasi, whose
prison and district headquarters were immediately below the citadel, had warehouses and workshops on the site for their motor pool until 1990. The rest of the citadel was unused and plants were allowed to naturally regrow.
Restoration After German reunification in 1990, a massive project to restore the citadel was begun. It is the largest such project undertaken by the Erfurt city council and it is funded by the city council and the
Thuringian state and German federal governments. Over 300 people were temporarily employed. Most buildings added since 1868 were removed, most earlier buildings, including the 12th century St Peter's Church, were restored or stabilised, ditches were cleared and walls and bastions were repaired, the
horchgänge (listening passages) were cleared, and the 1832 wood-fired fortress bakery was brought back into working order. As at January 2018, the restoration is still on-going. ==Main buildings and structures==