There are traces of Roman occupation including a fort, built in the late 300s AD, above the Alderneys only natural harbour. The Alderney Nunnery was probably located on the site of this one best preserved Roman forts in the British Isles.
The 26-foot tall Roman tower features 10-feet-thick walls. Built of stone and Roman concrete, many of the outer walls are still standing however only fragments remain of the tall tower that would have stood inside the walls, there is a similarity to Roman signal stations built in Yorkshire.
The British are believed to have refurbished the Roman fort in 1793, leveling off the tower walls in the process, according to Heritage Daily. When the German’s invaded the island it appears they inserted a Type 501 bunker neatly between the tower ruins, using the north and south internal walls effectively as shuttering to pour their concrete, according to Dr. Jason Monaghan, who is helping lead the excavation efforts.
The site is newly opened after a major make over. There are story boards, an information room, large WWII bunker and much, much more to explore on this amazing heritage site.
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.