1) Castle architecture 2) Castle in Japan 
The large main tower of a Japanese castle.
(from the article `arts, East Asian`) The general castle layout consisted of a donjon, or reinforced tower, called the tenshu, around which were arranged gardens, parks, and fortified ...
Donjon,Castle keeps, popular in the later 16th Century. The first castle keep was built by Matsunaga Hisahide in 1567 at Tamon. Tenshus were ultimately designed as much for appearance as defensive capability.