The peak Tokyo hikers say without meaning to
Mt. Tanzawa (1,567 m / 5,141 ft) sits at the heart of the Tanzawa mountains — the largest single mountain block in greater Tokyo's backcountry, roughly 40 km east-to-west and 20 km north-to-south, accounting for about a sixth of all the land in Kanagawa Prefecture. When Tokyo-area hikers say 'Tanzawa' — meaning a day trip, a sunrise hike, an after-work training climb — they usually mean Tonodake (1,491 m), the dramatic ridge-end peak two hours closer to the trailhead. But the peak the famous list-keeper Fukada Kyūya selected for his 100 Famous Mountains is not Tonodake. It is this one, in the middle of the main ridge, another two hours further in.
That two-hour difference is where the experience changes character. Tonodake on a clear weekend is a small festival — hundreds of climbers, summit chai, a tea-house line of selfies. Past the col of Ryūgabanba, the day-hikers drop away and the beech forest closes in. You climb gradually rather than steeply, the bird calls get clearer, and somewhere around the broad meadow before the summit you realise you've stopped seeing other people for fifteen minutes. Standing on Mt. Tanzawa is what it means to treat the Tanzawa range as a continuous mountain block rather than a day-hike playground.
Four trails, one summit
The classic line is the Ōkura-onē route — the 'Fool's Ridge.' Take the Odakyū Line to Shibusawa, the bus to Ōkura trailhead (290 m), and climb roughly 1,200 m of relentless ridge to Tonodake, then push north another two hours along the main ridge to Mt. Tanzawa. Round-trip from Ōkura: 4h40 up, 3h20 down. The 'Fool's Ridge' nickname is genuinely deserved — the climb is monotonous, sustained, and famously used by Tokyo-area hikers as a Himalayan altitude-training proxy.
The shortest route is the Tennōji-onē route from Shio-mizu-bashi (540 m) on the northern side, climbing the Honya-gawa valley and the Tennōji ridge to the summit in about 3h30. It is the standard choice for drivers — reach the trailhead via the Tōmei Expressway and bus from Hon-Atsugi to Sakkari, then a taxi to Shio-mizu-bashi. The eastern Miyagase route from Lake Miyagase traverses the Tanzawa Sanpō ridge for about 5h55 — long but gentle, the choice for hikers who love forested ridgewalks. A more dramatic option starts from Yabitsu Pass and follows the Omote-onē (front ridge) over Sannotō, Karasuotō and Gyōja-ga-take to Tonodake, then north to Mt. Tanzawa — the most scenic line in the Tanzawa range.
Getting there from Tokyo
Tanzawa is exceptionally accessible by Japanese mountain standards. From Shinjuku, the Odakyū Line reaches Shibusawa Station in about 80 minutes; the Kanachū bus from the station to the Ōkura trailhead takes 15 minutes more. Leaving Shinjuku before 6 a.m. puts you on the trail by 8 a.m. — fit hikers do the round trip to Mt. Tanzawa as a long day, though most stay overnight at the summit hut. The Hakone Express buses run reinforced timetables on weekend mornings from spring through autumn. By car, the public lot at the Hadano-Tokawa Park complex holds about 200 cars and fills before 6 a.m. on autumn weekends.
Beech forest, deer, and leeches
Above 800 m, the Tanzawa range is a deciduous forest of Japanese beech (Fagus crenata) and Mongolian oak. The ridge between Tonodake and Mt. Tanzawa, in particular, runs through old-growth beech that turns translucent green in mid-May and amber-gold in late October. Less visible at first but impossible to miss for long is the impact of Tanzawa's deer overpopulation: more than 4,000 sika deer inhabit the range, and the understory in many sections has been grazed down to bare soil. Kanagawa Prefecture installs deer-exclusion fencing along the ridge to allow seedlings to recover — you'll see the green netting along almost every trail.
Tanzawa is also famous, slightly unwelcomely, for its yamabiru (mountain leeches) — small, blood-feeding land leeches that infest the lower-elevation valleys (below about 800 m) from April through November. They are concentrated around the Shio-mizu-bashi, Miyagase and Yabitsu lower-route trailheads. Wear gaiters or knee-length socks, treat your boots with insect-repellent spray, and check yourself at every rest stop. The Ōkura ridge is the route least affected because most of its length is above the leech zone.
Miyama-sansō — the case for staying overnight
The summit holds Miyama-sansō, a mountain lodge with about 60 beds, open year-round. The hut was rebuilt in 2004 on the site of the original lodge, which was established after Tanzawa hosted the 1955 National Athletic Meet (Kokutai) mountaineering event — the event that effectively introduced the range to Japan's broader hiking public. Miyama-sansō has a strong local reputation: well-prepared dinners using Kanagawa-grown ingredients, hot showers when conditions allow, and one of the most courteous welcomes in greater Tokyo's mountain-hut network. Weekend reservations fill weeks in advance during foliage season.
What you get for staying is not the summit view — Tanzawa's summit is forested and modest by Japanese 100-Mountains standards. What you get is the quiet. Once the day-hikers go down to Tonodake or back to Ōkura, the ridge is yours: deer barks at dusk, the city haze far below, and a clear Mt. Fuji on the western horizon at dawn. Few places this close to a city of 14 million sound this empty after dark.
What to bring
Treat Tanzawa as a mid-grade mountain, not a beginner hill. The elevation is modest at 1,567 m but the distance and cumulative climb rival Japanese Alps approaches. Mid-cut hiking boots, a 20–30 L pack, long sleeves, a breathable rain shell, and gloves in cooler months. Microspikes are essentially required from December through March — the high ridge ices over every winter even when there is no real snowpack. Spring (May new-green) and late autumn (late October beech foliage) are the best seasons; summer is hot, humid and leech-active and rarely recommended. Water is sold at the summit huts (Miyama-sansō, Sonbutsu-sansō on Tonodake), but reliable natural sources are sparse — carry 2 L in summer and 1.5 L in winter.
The 1955 National Athletic Meet mountaineering event is, in a real sense, the founding moment of modern Tanzawa hiking. Before it, the range was forestry country with a thin network of unmaintained trails. The hut system (Miyama-sansō, Sonbutsu-sansō, Hiruba-take-sansō) and the modern signage all descend from the infrastructure built for that event. Almost everything an Ōkura-ridge hiker sees today was, in some form, set in motion by Japan's post-war national sports calendar.
What's beyond
From Mt. Tanzawa, the natural extension is north-west along the main ridge to Mt. Hiru-ga-take (1,673 m), the highest peak of the entire Tanzawa range — about 2h30 from Tanzawa summit. The classic two-day plan stays overnight at Miyama-sansō, traverses to Hiruga-take in the morning, returns and descends to Ōkura by mid-afternoon. Further west, Mt. Hinokibora-maru (1,601 m) hosts the most spectacular azalea bloom in the Kantō region — late May to early June, when Shiroyashio and Tōgoku-mitsuba-tsutsuji turn the upper ridge white and red. Tonodake → Tanzawa → Hiru-ga-take → Hinokibora-maru in three days is the canonical 'full Tanzawa traverse' and remains one of the great training routes for Japanese Alps trips.
