Sōdaijō was the fortified mountain redoubt, a ridgetop fort, which made up a jōkan (castle-residence) pairing with the Hoshina-yakata on the plain below. Sōdaijō was the central fort in a complex of fortifications which include Hoshina-Maenoyama-toride on the lower ridge. First constructed in the 15th century, Sōdaijō's lord was Hoshina Masatoshi, and the castle fell to Murakami Yorihira in 1513.
Sōdaijō was constructed impressively with stone-piled ramparts by incorporating ancient masonry purloined from pre-existing burial mounds on the mountain. These earthen structures became incorporated into the castle's defensive profile. A detached bailey of Sōdaijō can be found on the ridge above the castle which served as a monomidai (look-out platform).
Sōdaijō is a yamajiro (mountaintop castle) ruin in the Wakaho Township of Nagano Municipality. The ruins feature kuruwa (baileys), dorui (earthen ramparts), horikiri (trenches) and ishigaki (stone walls). The ishigaki is most prominent on the southern side of the forward bailey complex. It appears to have been constructed by cannibalising kofun (ancient tumuli), at least in part. One portion of the ishigaki even appears to retain a small entrance way to a tomb. Other baileys can be found further up the ridge, and these are separated by horikiri. Sōdaijō also has a dejiro, a sort of annex or detached bailey, located even further up the ridge, which likely served as a look-out.
|English Name||Soudai Castle|
|Year Founded||15th Century|
|Castle Condition||Ruins only|
|Historical Period||Pre Edo Period|
|Artifacts||Horikiri, Ishigaki, Kuruwa|
|Features||trenches, stone walls|
|Access||Take the trail to Mount Tarou; climb from Hoshinamaeyama-toride.|
|Visitor Information||24/7 free; mountain|
|Time Required||60 minutes|
|Location||Nagano, Nagano Prefecture|
|Coordinates||36° 35' 45.74" N, 138° 15' 48.24" E|
|Added to Jcastle||2023|
|Admin Year Visited||Viewer Contributed|
|Friends of JCastle|