Mercedarian monastery of San Juan de Poio was built in the 17th century and reflects the taste for combining Classicist and Baroque styles. The first document of the monastery on the site is however much older, dating from 942 AD.
Inside, there is a splendid retable from the 18th century, in Churrigueresque style, and the tomb of St. Trahamunda is in the left-hand aisle (much venerated in the district). The procession cloister (16th century) is also noteworthy, with a Baroque fountain and an original stairway. Also worth mentioning are the library, the museum of mosaics, the Escola de Canteiros or the centre for the Summer University courses. The monastery is currently devoted to tourist accommodation, governed by the nuns.References:
The Petersberg Citadel is one of the largest extant early-modern citadels in Europe and covers the whole north-western part of the Erfurt city centre. It was built after 1665 on Petersberg hill and was in military use until 1963. It dates from a time when Erfurt was ruled by the Electors of Mainz and is a unique example of the European style of fortress construction. Beneath the citadel is an underground maze of passageways that can be visited on guided tours organised by Erfurt Tourist Office.
The citadel was originally built on the site of a medieval Benedictine Monastery and the earliest parts of the complex date from the 12th century. Erfurt has also been ruled by Sweden, Prussia, Napoleon, the German Empire, the Nazis, and post-World War II Soviet occupying forces, and it was part of the German Democratic Republic (East Germany). All of these regimes used Petersberg Citadel and had an influence on its development. The baroque fortress was in military use until 1963. Since German reunification in 1990, the citadel has undergone significant restoration and it is now open to the public as a historic site.