Noun
The chief tower, also called the keep; a massive tower in ancient castles, forming the strongest part of the fortifications. See Illust. of Castle.
Source: Webster's dictionaryCultural legacy A replicated Osaka Castle has been created on the site of Hideyoshi's great donjon. Source: Internet
Converted into a donjon around 950, Château de Doué-la-Fontaine in France is the oldest standing castle in Europe. Source: Internet
"Dungeon" is a corrupted form of "donjon" and means a dark, unwelcoming prison. Source: Internet
The larger towers provided space for habitation to make up for the loss of the donjon. Source: Internet