Awarded 523,000 koku for his loyalty at Sekigahara, Kuroda Nagamasa abandoned the old Najima Castle and built afresh on the Fukusaki coast. Construction took seven years. A tenshu was apparently planned but never raised — most historians attribute this to political deference to the Tokugawa shogunate. Demolitions after the 1873 Castle Abolition Order left only stone walls and a few turrets; today it lives on inside Maizuru Park, woven into the city's everyday life.
A teikaku-shiki layout: the inner bailey surrounded by ringed second and third baileys. The northern moat connects directly to Hakata Bay, designed for resupply by sea. The stone walls use uchikomi-hagi technique by masons summoned from across the country — state-of-the-art for the time. The tenshu base is fully built; the keep that should have stood on it never came.
A defense-in-depth philosophy: draw the enemy in, then disorient them across multiple baileys before annihilation. Reaching the inner ward requires three forced changes of direction and elevation. It is information warfare expressed as urban planning — an attacker loses positional sense before reaching the core.
Choosing function over symbol still teaches modern cities and organizations. Preferring usage (the nawabari) over ownership (the tenshu) anticipates the SaaS-era debate of access vs. ownership. Fukuoka Castle's deepest design question was "how to make power less visible."
About a 15-minute walk from Maizuru Park's main entrance to the inner ward site. Walking the perimeter reveals the nawabari intent more clearly than walking inside. The relationship between the third-bailey north moat and the modern street grid is especially telling. Open to locals as a jogging route — the texture of a castle that never got touristified.