The original Oshi Castle was never captured by conventional force, only yielding after the surrender of Odawara Castle.
The nickname 'Floating Castle' (Oshi-no-ukishiro) refers to how the castle appeared to float above the marshes when flooded by enemy siegeworks.
The current Gosankai Yagura was rebuilt in 1988 to serve as the museum facility.
The siege of 1590 involved Ishida Mitsunari attempting to flood the castle by constructing a 28-kilometer canal, which failed and backfired against the attackers.
The site remains a focal point for the 'Oshi Castle Jidai Matsuri,' a festival reenacting the castle's history.
Oshi Castle Gosankai Yagura is a reinforced concrete reconstruction of the three-story turret that once served as the central keep of the historical Oshi Castle. The original fortress famously resisted Ishida Mitsunari’s forces during the 1590 Siege of Oshi by leveraging the surrounding marshlands, earning it the nickname 'Floating Castle.' The current structure functions as the Gyoda City Local Museum, housing artifacts related to the castle's military history and local traditions. Visitors can ascend to the top floor to view the surrounding Saitama plains. The grounds integrate remnants of the original earthworks and defensive moats. The museum provides context on the historical significance of the castle in the context of the Sengoku period. Exhibits include weaponry, documents, and historical models of the fortification.
The view from the base of the Gosankai Yagura looking up at the turret across the reflective pond.
Visit the adjacent museum galleries to understand the engineering behind the failed 1590 flood attack.
Walk the perimeter of the park to see the preserved earthen embankments and moat sections.
Check local event calendars for the annual autumn historical festival held on the castle grounds.
Assuming the current structure is an original wooden feudal-era building rather than a modern concrete reconstruction.
Typically closed on certain days of the week, often Mondays; closed during year-end holidays.
Remove shoes when entering the interior of the turret/museum building; photography may be restricted in specific exhibit rooms.
