Stolzenfels was built initially from 1242 by the Archbishops & Elector-Counts of Trier, directly opposite and intended as a counterweight to Castle Lahneck on the other bank of the Rhine, built slightly before the Archbishop & Elector-Count of Mainz. (Both Stolzenfels & Lahneck have the unusual feature of a five-sided main Keep, with the angled site directed at the most likely avenue of attack to deflect incoming projectiles).

The Castle's history was mostly uneventfull before the 17th Century, expanded twice to serve as a toll-both for the road and river.

Then it was first heavily damaged during the 30-years war after rapidly switching hands 4 times, until it was completely abandoned following further destruction by french troops in the Nine-years war (1689). In 1802 it became property of the city of Koblenz, who gifted it to Crown-Prinz Frederick-Willima of Prussia shortly after his marriage to Elisabeth of Bavaria in 1823.

Frederick was an early enthusiast in the beginning "Rhine-romantic" and had financed the construction of the nearby romanesque Revival-church St. Menas as a gift to the town of Stolzenfels. In 1836, he contracted Karl-Friedrich Schinkel, the go-to Architect of prussian royalty and responsible for much of the buildings in Berlins Center at the time, with reconstructing the Castle as a summer-residence for himself and his wife. Schinkel was explicitely advised to keep all remaining medieval structures intact and merely repair them, aswell as to add another wing to the Palas on the other side of the Courtyard, and dressing the ensemble up in the english neo-gothic aesthetic.

The one exemption was the curtain-wall behind the Palas: It and its tower had survived mostly intact, but Frederick had one opening made in the wall to create a direct sightline from the garden to the new Fortress Ehrenbreitstein in Koblenz. After Schinkels death in 1841, Friedrich Stüler finished the construction (adding the massive Gothic Chapel on the rhine-side for Fredericks wife). He'd later also lead the reconstruction of Castle Hohenzollern itself.

Frederick had the castle furnished with a mix of genuine medieval artifacts from his personal collection aswell as newly made faux-medieval furniture (aswell as giving his wife the larger & more well-lit quarters situated rhinewards that had been intended for him). Despite the immense personal investment into the Castle, Frederick only visited it 7 times. However, he decreed that the public was allowed to tour it as long as he wasn't currently residing in it, giving the castle an unbroken 180 year long tradition of tourism.

Made this with my DJI mini 5 pro after closing hours.

By @ rebet

Only accessible by boat this tiny island has a castle and a pub. The landlord of the pub is known as the King of Piel island.

Hallforest Castle is a keep, one of the oldest in Scotland. The castle is believed to have been built by Robert the Bruce as a hunting lodge; he is said to have granted it to Robert II Keith, Marischal of Scotland, the predecessor of the Earls of Kintore. Mary, Queen of Scots visited Hallforrest in 1562.

In North East England, beautiful 12th century castle ruin