The Neue Schloss on a hill to the N. of the town founded in 1479 enlarged in 1519 and dismantled in 1689 was afterwards partially restored.
It is now a summer-residence of the Grand Duke and is comfortably fitted up containing some good modern pictures carving family-portraits etc. The curious subterranean vaults with stone and iron doors were probably once used as dungeons. 

Bædeker The Rhine from Rotterdam to Constance (1873) Route 34 page 196

HOHENBADEN OLD CASTLE - Altes Schloss Hohenbaden, is high above Baden-Baden and one of three castles that defended the most prized territory of the Margraves of Baden, from the 11th - 15th century. Built in 1102, today its ruins and those of the newer "extension", Unterburg (lower castle) from the late 14th century, offer spectacular views over Baden-Baden, the Black Forest and the Rhine Valley.

The Mausoleum of Hadrian, usually known as Castel Sant'Angelo (Italian pronunciation: [kaˈstɛl sanˈtandʒelo]; English: Castle of the Holy Angel), is a towering cylindrical building in Parco Adriano, Rome, Italy. It was initially commissioned by the Roman Emperor Hadrian as a mausoleum for himself and his family. The building was later used by the popes as a fortress and castle, and is now a museum. The Castle was once the tallest building in Rome.
https://en.wikipedia.org/wiki/Castel_Sant%27Angelo

From Bædeker's Rhine - 1873: Route 45 page 238
The line runs parallel with the mountains of the Black Forest. In the distance to the 1. rises the grand-ducal castle of Staufenberg, founded in the 11th cent. by Otho of Hohenstaufen, Bishop of Strassburg, and still in good preservation.

On a rocky eminence 2 M. to the N.E. of the Alte Schloss, and above the village of Ebersteinburg, are the ruins of *Alt-Eberstein {Ebersteinburg 1601 ft.), which, like the Yburg (p. 197), was once a Roman watch-tower.

Dilsberg Castle (German: Bergfeste Dilsberg) is a castle on a hill above the River Neckar in Neckargemünd, Germany. The castle was built by the counts of Lauffen in the 12th century. In the 13th century it became the main castle for the counts. In the 14th century it became part of the Electorate of the Palatinate and received town rights in 1347. During the Thirty Years' War, the castle was considered impregnable until Imperial forces under Tilly took the castle in 1622 after a long siege. In 1799, French forces tried and failed to storm the castle.

Chillon Castle (French: Château de Chillon) is an island castle located on Lake Geneva (Lac Léman), south of Veytaux in the canton of Vaud. It is situated at the eastern end of the lake, on the narrow shore between Montreux and Villeneuve, which gives access to the Alpine valley of the Rhône. Chillon is amongst the most visited castles in Switzerland and Europe. Successively occupied by the house of Savoy then by the Bernese from 1536 until 1798, it now belongs to the State of Vaud and is classified as a Swiss Cultural Property of National Significance.

Warwick Castle is a medieval castle developed from a wooden fort, originally built by William the Conqueror during 1068. Warwick is the county town of Warwickshire, England, situated on a meander of the