n. 城堡主楼

[ noun ]
the main tower within the walls of a medieval castle or fortress
<noun.artifact>

Donjon \Don"jon\ (d[u^]n"j[u^]n), n. [See {Dungeon}.]
The chief tower, also called the {keep}; a massive tower in
ancient castles, forming the strongest part of the
fortifications. See Illust. of {Castle}.