Nagoya Castle Keeps, Nagoya

Nagoya Castle, renowned for its distinctive "connected-keep" architecture, features a main keep with five stories on different levels and a smaller keep of two levels connected by an abutment bridge. This unique design adds to the castle's historical and architectural significance. Evidence suggests that another small keep was initially planned for the west side of the main keep, as indicated by traces of an entryway in the upper stone wall foundation. However, during construction, the entryway's location was changed to its current position, leaving remnants of the original plan embedded in the stonework.

The keeps served practical defensive functions, with the first level of the main keep used for storing various weapons, while flammable materials like gunpowder were kept outside the castle to reduce fire risk. Tragically, both the main and small keeps were destroyed during World War II but were reconstructed in 1959 using modern materials such as steel beams and concrete. In 2017, a donation drive was launched to rebuild the keeps using wood, based on the original plans, with the aim of completing the main tower by 2022.

The construction of the castle's impressive stone walls was a collaborative effort among twenty feudal lords, including Katō Kiyomasa, who oversaw the building of the keep's walls. The foundation stones bear inscriptions from the family members involved, a testament to the craftsmanship and labor invested. The stone wall supporting the keep employs a technique known as "ogi kobai" or "fan sloping," where the upper part curves outward like a fan. This design, also referred to as the Kiyomasa-style Crescent Stone Wall, helps prevent wall swelling by balancing the stone weight against the internal pressure of sand and earth.

A notable feature between the main and small keeps is a roofless corridor with earthen and stone walls. The outer part of the west side of this corridor is lined with 30-centimeter-long spearheads, designed to deter enemy troops from climbing over the eaves. Similar defensive structures, including a sword-fence, are present at the Fumei Gate on the east side of the main keep, highlighting the castle's strategic design elements aimed at thwarting potential attackers.