Calenberg Castle (, later called Schloss Calenberg and Feste Calenberg; ruins known as Alt Calenberg) was a medieval lowland castle in central Germany, near Schulenburg in the borough of Pattensen, 13 km west of the city of Hildesheim. It was built as a water castle in 1292 by the Welf duke, Otto the Strict, in der Leine river meadows between 2 branches of the Leine river on the southern part of the chalk marl hill of the Calenberg. At the start of the 16th century it was converted into a fort (Feste). In the 15th century, Fort Calenberg gave its name to the Welf Principality of Calenberg. Following the Thirty Years' War it lost its military importance and was slighted. Today it is a ruin with underground vaults that are surrounded by high ramparts. Etymology The word Feste or Veste ("fort") stems, like the words Festung ("fortress") and Befestigung ("fortification") from the adjective fest ("strong", "firm" or "immovable"). The adjective in turn has its roots in the Middle High German and Middle Low German word veste and the Old High German word festi meaning: fortress, castle, fortification and security of a location. The word syllables Kal, Kalen-, Calen- in the word Calenberg are derived from the word kal in the Middle High German and Middle Low German languages and mean "bare", "stripped" or "treeless". The name formations with Kal, Kalen or Calen could refer to the geological base of rock or stone. So the word Calenberg means the same as kahler Berg or "bare hill". The following variations have been noted: dat hus to der kalenborch 1327, dat slot kalenberch 1350, ...unse del des slotes der Kalenborch 1363, to dem Kalenberge, unse Slot de Kalenberch 1406, Haus Calenberg 1661, Fürstl. Ambtshaus, Fürstl. Palladium 1663, Altes Schloß Calenberg 1730, Auf dem Alten Calenberg 1777, Alt Calenberg 1854, Alt-Kalenberg 1896. Location on the Calenberg The castle site stands on a low hill, the Calenberg, which is . The hill was formed almost 100 million years ago at the beginning of the Upper Cretaceous during the Cenomanian stage. Before the castle was built, the Calenberg rose some 10 metres above the water meadows between the river arms of the Leine that existed at that time It covered not just the site of Calenberg Castle, but extended a further 500 metres further north to the River Leine. As a result, the castle moats had