Dolbadarn Castle is a fortification built by the Welsh prince Llywelyn the Great during the early 13th century, at the base of the Llanberis Pass, in northern Wales. The castle was important both militarily and as a symbol of Llywelyn's power and authority. The castle features a large stone keep, which historian Richard Avent considers the finest surviving example of a Welsh round tower. In 1284 Dolbadarn was taken by Edward I, who removed some of its timbers to build his new castle at Caernarfon.
The remaining parts of the castle continued to be used as a manor house into the 14th century. By the 18th century, however, Dolbadarn Castle was ruined and uninhabited. From the 1760s onwards, however, it became a popular topic for painters interested in the then fashionable landscape styles of the Sublime and the Picturesque. J. M. W. Turner's 1800 work Dolbadarn Castle depicted the back-lit castle looming over the landscape and became particularly famous, but the paintings of the castle by Richard Wilson and Paul Sandby also represent important artistic works of the period.
References:Ehrenbreitstein Fortress was built as the backbone of the regional fortification system, Festung Koblenz, by Prussia between 1817 and 1832 and guarded the middle Rhine region, an area that had been invaded by French troops repeatedly before. The fortress was never attacked.
Early fortifications at the site can be dated back to about 1000 BC. At about AD 1000 Ehrenbert erected a castle. The Archbishops of Trier expanded it with a supporting castle Burg Helferstein and guarded the Holy Tunic in it from 1657 to 1794. Successive Archbishops used the castle's strategic importance to barter between contending powers; thus in 1672 at the outset of war between France and Germany the Archbishop refused requests both from the envoys of Louis XIV and from Brandenburg's Ambassador, Christoph Caspar von Blumenthal, to permit the passage of troops across the Rhine.