Iwakurajō is said to have been originally built by the Mabuchi Clan in the Muromachi period. The Nagahara Clan, who built neighbouring Koźutsumijō, were vassals of the Mabuchi Clan who would surpass them and enter into a direct master-retainer relationship with the hegemonic Rokkaku Clan. Thus it is that Iwakurajō is also referred to as 'the old castle' in relation to Koźutsumijō on the opposite peak. Iwakurajō is atypical in that rather than being built on the ridge, the ridge is utilised as a bulwark with the castle's main baileys built into a hollow beneath it.
Iwakurajō is a satellite castle of Koźutsumijō (Kozutsumi Castle). It's an intriguing site. One ascends to the site of the castle and there is a ridge. It seems like a very scrawny, narrow bailey, until one looks to one's left and realises that this ridge acts as large wall of earth for the real bailey complex which is situated below. Essentially there is one bailey surrounded by this tall dorui carved from the mountain's ridges. There is terracing beneath the dorui on the inside though, creating sub-baileys above the main bailey (usually sub-baileys are found below not above the central bailey). This set-up is a sort of inversion of what we would expect from a yamajiro (mountaintop castle), like a yamajiro turned inside-out! The site then takes on the qualities of the truly mysterious because at the centre of the bailey is a pond. This pond has a channel from which water is slowly drained off, yet it is said to never empty. Presumably the water wells up from some place below, as it cannot possibly be fed from any streams above in this strange, craterous space. This means that the defenders of Iwakurajō never lacked for a water source, which is one of the most important considerations of siting a castle.
|English Name||Iwakura Castle|
|Year Founded||Muromachi Period|
|Castle Condition||Ruins only|
|Historical Period||Pre Edo Period|
|Artifacts||Dorui, Kuruwa, Koguchi, Hori, &c.|
|Access||Hike from Koźutsumijō|
|Visitor Information||24/7 free; mountain|
|Time Required||40 minutes|
|Location||Yasu, Shiga Prefecture|
|Coordinates||35° 3' 56.02" N, 136° 3' 37.44" E|
|Added to Jcastle||2022|
|Admin Year Visited||Viewer Contributed|
|Friends of JCastle|