The Roman Forum of Thessaloniki is the ancient Roman-era forum of the city, located at the upper side of Aristotelous Square. It is a large two-terraced forum featuring two-storey stoas, dug up by accident in the 1960s. The forum complex also boasts two Roman baths, one of which has been excavated while the other is buried underneath the city, and a small theater which was also used for gladiatorial games. Although the initial complex was not built in Roman times, it was largely refurbished in the 2nd century. It is believed that the forum and the theater continued to be used until at least the 6th century.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.