The Heidetränk Oppidum near Oberursel is one of Europe"s most important Celtic oppida. The oppidum was surrounded by ramparts which encircled the settlement of opposite sides of a ravine called the Heidetrankthal. This imposing rampart where 10 km long and had six gates. The high point of the settlement was in the late La Tène period, but lost its importance in the mid first century BC. Archaeological finds from the Heidedtrank Oppidium include agricultural implements such as plowshares, hoes, scythe and sickle blades as well as tools and Celtic coins, particularly the so-called 'Nauheim Quinarius', which was probably coined in the oppidum itself.
References:Château de Niort is a medieval castle in the French town of Niort. It consists of two square towers, linked by a 15th-century building and dominates the Sèvre Niortaise valley.
The two donjons are the only remaining part of the castle. The castle was started by Henry II Plantagenet in the 12th century and completed by Richard the Lionheart. It was defended by a rectangular curtain wall and was damaged during the Wars of Religion. In the 18th century, the castle served as a prison.
The present keeps were the central point of a massive fortress. The southern keep is 28m tall, reinforced with turrets. The northern tower is slightly shorter at 23m. Both are flanked with circular turrets at the corners as well as semicircular buttresses. Each of the towers has a spiral staircase serving the upper floors. The Romanesque architecture is of a high quality with the dressed stones closely jointed.