Mt. Iwabitsu

Published: Aug 11, 2026

Updated: Aug 11, 2026

Mt. IwabitsuSanadacastle ruinshikingHigashiagatsuma

Representative image — not a photograph of this location.

Mt. Iwabitsu is 802 metres of broken rock rising straight out of the Agatsuma valley, with a sheer south face that makes it look considerably bigger than it is. On its slopes are the earthworks of Iwabitsu Castle, a Sanada stronghold — this was Sanada Masayuki's mountain fortress, and it is where the young Sanada Nobushige, later famous as Yukimura, is said to have spent part of his childhood. The castle was one of the three great mountain castles of the Kanto region and never fell to assault.

What survives is not buildings but terrain: cut ridges, dry moats, and the bailey platforms, reached in about fifteen minutes from the trailhead. Continuing to the summit turns the walk into a real scramble with chains and exposed rock in places, and the reward is a view down the whole valley toward the Agatsuma river. The mountain is well known within Gunma and to castle enthusiasts, and essentially unvisited by anyone else.

Essential Information

Opening Hours

Trails open at all times | Trailhead information centre 9:00 AM – 4:00 PM (April–November)

Closed: Information centre closed December–March | Trails accessible year-round, upper sections hazardous in snow and rain

Entrance Fee

Free | Free trailhead parking (around 80 spaces)

Best Season

Late April–May and October–November | Late autumn for clear valley views

Visit Duration

45 minutes for the castle ruins | 2.5–3.5 hours for the summit round trip

Getting There

Access Information

Higashiagatsuma, Agatsuma District. Free trailhead parking for around 80 cars at the Hirasawa trailhead, elevation about 500 m. Around 15 minutes on foot from the trailhead to the castle's main bailey; the summit is a further steep scramble with chain sections. The Hirasawa trailhead information centre (1965-2 Haramachi) is open 9:00 AM – 4:00 PM April–November and closed December–March. Free to climb.

Insider Guide

Premium

**Two very different walks share one trailhead.** The castle ruins are an easy fifteen minutes on a graded path and are suitable for anyone. The summit is a scramble on rock with chains and drops, and it is not a casual continuation of the first walk. Decide which one you are doing before you start. **Ridge route or valley route.** The path splits almost immediately into the one-ne (ridge) and sawa (valley) trails. The ridge route is more exposed with better views; the valley route is sheltered and easier underfoot. Going up one and down the other is the standard local loop. **Read the earthworks, not the ruins.** There is nothing standing. What you are looking at is deliberately shaped ground — cut ridges to break an approach, dry moats, and stepped platforms. Once you can see the shaping, the defensive logic of the site becomes obvious. **The information centre is seasonal.** It opens 9:00 AM to 4:00 PM from April to November and shuts completely for the winter. Maps and current trail conditions come from there, so a winter visit means arriving without them. **Boots for the summit, in any season.** The rock is broken and the chain sections are genuinely steep. In wet weather the upper mountain is not a good idea at all.

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