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 Walls The citadel is surrounded by 2,180 metres of stone walls, which were erected in the first building phase, beginning in 1665. They form the star-shaped ground plan of the citadel, made with eight bastions and four ravelins and are between 1.2 and 6 metres thick, and from 8 to 26 metres high. There are small look-out towers built into the walls. There are now only three ravelins as Ravelin Wilhelm was removed in the 19th century. There are tunnels within the walls, called the Horchgänge in German, meaning the 'listening passages'. At the time the citadel was first built there were no trenches or moats beyond the wall, so the Horchgänge were constructed so that soldiers could walk through them to listen for anyone trying to tunnel into the fortress. Gate and Commandant Building (Peterstor & Kommandantenhaus) The Peterstor, the main entrance to the citadel, was built from 1666 to 1668. It was designed by Antonio Petrini and bears the coat of arms of Johann Philipp von Schönborn (1605–1673), the Archbishop-Elector of Mainz. In 1993 the two wooden portcullis were reconstructed within the double archway entrance. The script above the gateway which reads "Citadelle Petersberg", was installed in 1861. The Commandant Building was built in 1669 by an Italian construction team. From 1939 to 1945 it was used as a military court by the Nazis. It was restored in 1998 and is now used by Tanztenne Petersberg, a dance school for traditional Thuringian folkdancing. St Peter's Church (Peterskirche) The Peterskirche, the 75 metre-long monastery church, was built between 1103 and 1147. It originally had two towers at its east end, which along with the towers of the Erfurt cathedral and the Severikirche, dominated the city