Tenshu

Tenshu, written 天守, is the central keep or main tower of a Japanese castle. It is usually the tallest and most fortified structure within a fortress, serving as both a residence for the lord and a symbol of authority. The tenshu stands at the heart of the castle’s layout, and the term distinguishes the principal keep from gates, walls, and secondary towers.

Historically, tenshu emerged during the Sengoku period as fortifications grew more complex. As castles evolved into multi-storied, stone-based complexes, the keep became the focal point for command and defense. The architecture typically features a raised stone base and several stacked wooden floors, with plastered walls and a tiled roof. Exterior ornamentation and interior arrangements were designed to project power and provide secure space for defenders and residents.

Many tenshu were lost to fires, earthquakes, or warfare; some were rebuilt or reconstructed in later periods. In some castles, the original design survives only partly, while others exist as modern reconstructions. Notable examples include Himeji Castle in Hyōgo Prefecture, whose tenshu is a UNESCO World Heritage Site and a National Treasure, and Matsumoto Castle in Nagano Prefecture, known for its close to original Edo-period keep and designation as a National Treasure. Some castles have their tenshu rebuilt in later eras.

Today, tenshu remain enduring symbols of Japanese castle architecture, reflecting historical power, aesthetics, and regional identity. They attract researchers and visitors as focal points of cultural heritage and tourism.