Lake Okutama: Tokyo's Mountain Reserve

Train: JR Chuo Line from Shinjuku to Tachikawa (30 minutes), then the JR Ome Line to Okutama Station (50 minutes, with direct trains on weekends). That's 80 minutes in total. The Ome Line only runs one or two trains an hour, so check the timetable and plan your connections before you leave.

Bus from Okutama Station: The Okutama-ko bus takes 20 minutes from the station to the lake. It carries on past the lake to the Mugiyama floating bridge stop (Ogouchi Shrine-mae) and further toward the Tozura bridge. Buses come roughly once an hour, so if you miss one you wait 60 minutes. Leave room for that in your day.

By car: Take the Chuo Expressway to Route 411, about 2 hours from central Tokyo. Weekdays are quicker, and weekend traffic on Route 411 can get heavy. Lakeside parking fills by 10am on summer weekends. The road up to Nippara Cave is extremely narrow, so take the public bus there instead of driving.

The dam that made Lake Okutama was finished in 1957. Before the water came up, the whole Ogouchi valley, with its farmland, homes, and a string of small shrines, went under what is now the lake's deep green surface. Ogouchi Shrine, on a forested peninsula reaching into the middle of the lake, was founded to enshrine all the village shrines lost to the water. It is a sort of memorial to what the valley gave up so Tokyo could have a reliable water supply.

Once you know that, the green water looks different, because it's sitting over what's left of a valley people lived in. Near the Ogouchi Dam Observatory, the Tokyo Metropolitan Government runs the Water and Greenery Friendship Hall (水と緑のふれあい館), which explains the history of the reservoir and the forests around it. Entry is free, and it's worth 30 minutes.

Lake Okutama has two floating bridges, Mugiyama (麦山の浮橋) and Tozura (留浦の浮橋), about nine minutes apart by bus. Mugiyama gets more visitors because it's near Ogouchi Shrine and looks toward Mt. Mito. Tozura is quieter and feels more remote.

Both sit on floating pontoons instead of fixed foundations, which is why they sway a little as you walk across. The reservoir level moves, rising after heavy rain and dropping in droughts, so a fixed bridge would end up too high or underwater depending on the season. A pontoon bridge rises and falls with the lake. Mugiyama was first floated on real steel drum cans, and that's why locals still call it the Drum Bridge (太鼓橋). The drums have since been swapped for resin and metal cylinders made to look like the originals. The 220-metre crossing takes about 10 minutes on foot.

Both bridges close when the water drops far enough that the deck sits too close to the lakebed, and when the wind is strong. They also close a handful of times a year for maintenance or weather. If the bridge is the main event of your day, check the Okutama Tourism Association website or call ahead first.

Nippara Stalactite Cave (日原鍾乳洞) is the largest limestone cave in the Kanto region and one of the most impressive natural sights inside Tokyo's boundaries. It runs 1,270 metres in total with 134 metres of height difference, dipping down and climbing back up, so the inside feels bigger than you expect. The Tokyo Metropolitan Government has made it a designated natural monument.

There are two sections. The old cave was a place of mountain worship for centuries, and legend says the monk Kobo Daishi used the hollow at its center for meditation. The new cave was found in 1962, when construction workers broke through a rock wall into a chamber that had been sealed for thousands of years. The two are now joined into one walking circuit.

The temperature inside stays at 11°C all year. In summer that's cold enough that you'll want another layer, and in winter it feels warm compared with outside. The stalactites and stalagmites took hundreds of thousands of years to form, and they're lit with colored lights that make the place half geology, half theater. One highlight is a suikinkutsu, a buried earthen jar placed so that dripping water falls into it and makes a clear, bell-like note that rings through the rock. It's an old feature of Japanese gardens, usually tea gardens, and finding one in a cave is strange and lovely.

The circuit takes 40 to 60 minutes at a comfortable pace. You have to duck in places, so wear shoes with grip, and on rainy days water runs freely through the cave, so bring a light waterproof layer. Admission is about ¥800 for adults and ¥500 for children. The cave is a 30-minute bus ride from Okutama Station on the Nippara bus, which doesn't run often, so check the schedule and know which bus you're taking back before you go in.

The Tama River runs through the Okutama valley, and how you use it depends on how much adrenaline you want.

The calm option is kayaking or canoeing on Shiromaru Lake (白丸湖), a smaller reservoir at Shiromaru Station, one stop before Okutama. OKUTAMA BASE and Shiromaru Village rent Canadian canoes there. They're stable and quiet, good for beginners or anyone who just wants to drift on green water between forested hills. Rental usually costs around ¥3,000 for two hours for a boat that holds up to three people, with life jackets and paddles included. The lake is calm in every season, and you don't need any paddling experience.

The river itself is more physical. Guided rafting and kayak tours leave from Mitake and Kawai stations (five and four stops before Okutama) on the Tama. A standard guided trip covers about 5km of river in roughly two hours, gentle enough for beginners and non-swimmers but fast enough to feel like you're really running a river. Companies such as River Joy work out of the Mitake area. Their bases are about 25 minutes' walk from the station, or you can arrange a shuttle in advance. Tours usually start from 9am, so getting to Mitake Station by 9:30am keeps things easy. If you're combining the river with the lake and the cave, give the river about half a day.

Hato-no-su Gorge (鳩ノ巣渓谷) is 20 minutes from Okutama Station, reachable by bus or a short walk from Hato-no-su Station. The trail follows the Tama River between steep rock walls and pools of clear water, and takes 1 to 2 hours at an easy pace with little climbing. In places the canyon narrows so sharply that the sound of the river fills it. It's the most dramatic scenery in the area, and anyone in decent walking shoes can do it.

For a longer walk, the Ikoi Trail runs 12km along the south bank of the reservoir from Ogouchi Dam to Yama-no-Furusato Village. It's rated easy, takes about four hours, and is open from mid-April through November. The village at the far end has a restaurant and traditional exhibits, and a bus back to Okutama Station.

The serious mountains (Odake, Mt. Mito, and the Okutama ridgelines) need proper footwear and experience. Those trails draw experienced hikers and are more than a casual day trip can take on.

Ogouchi Shrine stands on a forested peninsula that reaches into the middle of the lake, and you can see it from the floating bridge. Because it was founded to enshrine the village shrines the dam submerged, it is partly a guardian of Tokyo's water supply and partly a memorial. The view across the lake from the grounds is one of the better ones in the area. On the second Sunday of September the shrine holds its annual festival, with traditional performances by the old Ogouchi village communities.

Spring (April): Cherry blossoms around the lake usually peak in mid-April, about a week after central Tokyo because of the altitude. It's less crowded than comparable spots in the city, and blossoms against mountain ridges are worth the trip on their own.

Summer (June to September): Green, lush, and noticeably cooler than the city. Summer is when the river activities and the cave (a natural refuge at 11°C) make the most sense. Weekends in July and August bring crowds to the popular spots, so arrive before 9am or come on a weekday.

Autumn (late October to mid November): The ridges behind the reservoir start turning in late October, and peak color usually comes in the first two weeks of November. Go the week before the peak, when the color is already coming in and the crowds that follow it haven't arrived.

Winter (December to February): Quiet and cold, with the occasional dusting of snow. The floating bridge stays open in calm weather. It's a good season for photography, and the river activities stop until spring.

The relaxed day: Okutama Station → bus to Ogouchi Shrine-mae (Mugiyama floating bridge) → cross the bridge → bus or walk to the lakeside → Ogouchi Shrine → Water and Greenery Friendship Hall → bus to Nippara Cave → train back from Okutama. About 7 hours.

The active day: Mitake Station → rafting on the Tama River (half day, 9:30am start) → train to Okutama → Hato-no-su Gorge → bus to the floating bridge → dinner in Okutama town → last train back. 9 hours.

The cave-focused day: Okutama Station → bus to Nippara Cave (go early and beat the buses) → the cave circuit (60 minutes) → bus back to Okutama → Hato-no-su Gorge → lakeside café → evening train. Good in summer or on a shoulder-season weekday.

With a night stay: The Okutama area has traditional inns and mountain restaurants. Staying over lets you do the longer ridgeline hikes, and by late afternoon the day-trippers have gone home. Having the floating bridge to yourself at dusk is worth the extra night.

Infinite Tokyo can be built as a custom day trip that includes Okutama, with the cave and gorge in one direction or the lake and shrine in the other.

Can you visit Lake Okutama and Nippara Cave in the same day? Yes, if you watch the bus times. The Nippara bus from Okutama Station doesn't run often, and the bus between the station and the lake comes about once an hour. Plan your connections ahead with the Nishitokyo Bus schedule. The cave takes 45 to 60 minutes and the bus back to the station takes 30, so budget for both and don't assume the next bus is close.

Is the floating bridge open year-round? Mostly. It closes when the reservoir drops a lot in dry spells, in strong wind, and for maintenance several times a year. Check the Okutama Tourism Association website before you make the bridge the focus of your trip. Tozura and Mugiyama close under the same conditions but are managed separately, so one can be open while the other is shut.

Do I need experience for the Tama River rafting? No. The guided tours from Mitake and Kawai stations are set up for beginners, non-swimmers included. The operators supply the equipment, the safety briefing, and the guiding. The stretch of river they use is fast and fun without needing any technical skill. Children above a certain height and weight are usually welcome, but confirm with the operator when you book.

What is the temperature inside Nippara Cave? 11°C all year. In midsummer, when Tokyo hits 33 to 35°C outside, walking into the cave is a real shock to the system. Bring a light jacket whatever the season. On rainy days and for a day or two afterward, water runs freely through parts of the cave, so a waterproof jacket helps in wet weather.

Is Okutama worth it compared to Mt. Takao? They're different trips. Mt. Takao is quicker to reach, more developed, and has one clear trail to a summit. Okutama spreads more variety over a bigger area, with the cave, the floating bridge, the gorge, the reservoir, and the river, and it sees far fewer foreign visitors. For one focused hike, Takao is simpler. For a full day of different mountain sights well away from the tourist circuit, go to Okutama.