Ride Through a Reconditioned Historic Railway Tunnel in New Taipei’s Ruifang District

The old Sandiaoling Tunnel reopened in June 2022 as a walking and cycling route connecting Sandiaoling (or Houtong) with Mudan. It first went into operation as a train tunnel in 1922, but as freight volume and ridership on the line increased, the old single-width tunnel became insufficient. A neighbouring double-width one was constructed and the entrance to the original was bricked up. Decades later, when the New Taipei City government decided to utilise the ready-made tunnel by turning it into a path, the brick wall was torn down, revealing a whole world that had coalesced in the absence of human interference. There were colonies of bats using the tunnels as a roost, and the tunnel’s flooded floor was home to all sorts of aquatic life: fish, shrimp, crabs, and insect larvae. Plans were put on hold so that suitable environmental impact assessments could be carried out, and as a consequence of recommendations made in those assessments, the path has been constructed using methods that will reduce the detrimental impact on the tunnel’s residents. The end result is a really enjoyable walk accompanied by calming sights and sounds.

In the year or so since it has been open, it looks to have been rebranded as “The Dark Line,” but unfortunately (at time of writing), there’s still no English-language site to make booking easy for foreign visitors.

Distance: The version of this route that I did was about 15 km, but it’s possible to extend or shorten this ride (or walk) depending on how much time to have. To extend it, you can pretty much follow Keelung River the whole way from Taipei, and if you’re more into short and sweet, it can be shortened to about 6 km if you go straight from Houtong to Mudan.

Time: The whole ride from Ruifang to Shuangxi (coffee break included) took me about 2½ hours. I went at a really slow pace and stoped often.

Difficulty: 2/10 – This is easy for old-timers and new-comers alike. The route is well-signposted and exceedingly well-kept.

Total ascent: About 100m for the route I took. The majority of the route from Houtong to Mudan is on a slight downward slope, so it’s far easier than

Water: A single small bottle would suffice. There are cafés and places to stop in Houtong, Mudan and Shuangxi, so pack light.

Shade: It goes without saying that the tunnel section is so shady that even a vampire would feel at home. However, the sections outside of the tunnel are quite exposed.

Mobile network: Clear throughout.

Enjoyment: I would not hesitate to recommend this as a neat little day trip. I loved it. If you have more time, go on foot so that you can fully enjoy the peace and quiet of the tunnel.

Route type: Point to point.

Other: I wrote about this experience (briefly) in an edition of Travel in Taiwan Magazine. The rest of the article mentions several other attractions in Ruifang District that are also well worth your time.

Permit: After a brief sever-month period in which no application was necessary, it is now only possible to visit the tunnel if you apply online first.

Jump to the bottom of this post for a trail map and GPX file as well as ticketing and transportation information.

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I decided to start my journey from Ruifang rather than Houtong, the added distance isn’t all that far, and if I got tired later I could always only cycle back as far as Houtong and take the train from there.

Leaving the station via the main hall, take a left turn and head to the YouBike stand to the left of the exit. There are currently YouBike 1.0 and 2.0 available here, but if you want to ride all the way to Mudan or Shuangxi, you’ll have to pick the orange and white YouBike 2.0s.

Head east on the little lane that runs parallel to the tracks until you Minquan Street, turn right here, then almost immediately left onto Mindeng Road then set course for the blue arc of Ruifeng Bridge (瑞峰橋).

At the far end of the bridge turn left onto Sanzhaozi Keng Road and head against the current of the river. There is a traditional washing pool beside the river here that’s hidden from the road by the raised wall, and many residents had brought their bed linen out to dry in the late morning sun.

The most noteworthy feature on this little stretch of road has to be Ruifang Junior High School. It’s main building is a wide semicircle standing beyond the schools’s running track, and I was pleasantly surprised to note that Welsh was one of the languages featured in the welcome mosaic.

Beyond the school, the lane bends around to the right and you get to enjoy the first hilly view of the ride.

By Ruifang Sports Park keep heading straight onto the charmingly named Shezixing Road (蛇子形路, or Snake-shaped Road).

This single-lane road winds its way (much like its namesake), through pretty rural scenery.

A crested serpent eagle taking a short break.

By the time you rejoin the railway line, the road has ended and the cycle path turns left to head down and under the track. The chap taking a photo of this express train speeding towards Ruifang was a recent retiree who’d just returned back from years spent working in Indonesia. We cycled together for a while and he told me – gleefully – that he’d been retired for a year but that his wife still had to work, so he had lots of time to head out and explore.

The first time I visited this route was in April, the time when tung flowers cover the hills with patches of white. There is definitely a beguiling, timeless beauty in the sight of a farmer tending to their crops against the backdrop of spring blossoms.

As you near Houtong, you’ll find yourself entering the first of several tunnels.

Between the Ruifang side of the hills and the Houtong side of the hills, there are three short tunnels separated by short open sections. When I first came to try and cycle the Ruifang to Shuangxi route, this was as far as I got. The path on the far side of the tunnel had been blocked off for repairs, so all the photos after this point are from a return visit.

Emerging from the tunnels, you can see road, river, bike path and railway all lined up neatly together. Just before arriving in Houtong, you’ll pass this information centre on the right. (It has toilets.)

Houses perched on the banks of Keelung River beside Jieshou Bridge.

Of course, if you pass through Houtong, it is obligatory to pause so that you can admire the town’s friendly felines.

Once you’ve paid your tithe in pettings and suitably appreciative words, head straight through the town on its main (only?) street, passing the station on your right.

Houtong is comprised of two main sections of houses. The buildings gathered around the station are almost all used by small businesses, but the section of street a little further along is much quieter. Several of the properties have evidently been abandoned, but others are still used as residential properties.

Head through the village until you reach Fuxing Bridge. Cross Keelung River, then turn right onto Houtong Road. You’re likely to encounter some traffic here, so pay attention to your surroundings.

Even from the road, the area’s ramshackle rural beauty is evident. The river tumbles over eroded rocks, and old industrial buildings stand empty. You’ll know you’re nearing the tunnel when you spot Sandiaoling Train Station (photo on the right).

You might think that since this station is closer to the tunnel, it would make a better starting point for the journey, but it’s a little complicated. Sandiaoling Station isn’t connected to the road network at all, so to access the tunnel, you’d have to walk down along the Pingxi Line and cross a small railway bridge when you reach the village before doubling back up the far side of the river to arrive at the tunnel. Distance-wise, it’s probably a little shorter than coming from Houtong, and there is even a rack of YouBikes very close to the tunnel mouth, but I can’t advise you to come this way on account of the fact that it’s technically illegal. Almost everyone who gets off at Sandiaoling Station crosses that bridge. There are store owners who have to cross it in order to receive deliveries. But you can’t do it. The last time I visited Sandiaoling, I overheard a conversation between a couple of hikers and the station guard. The hikers asked the guard if there was any way to walk to the tunnel from the station. The guard looked shifty and told them there wasn’t. They asked about this bridge and he looked even more uncomfortable as he said that yes, it was physically possible to walk over it, but that anyone who did was running the risk of being photographed and fined. Given the laxness of regulations elsewhere, it seems vaguely ludicrous that this is the issue that authorities choose to double down on.

The start of the bikeway is just at the top of a short, steep incline. You’ll notice it because of the iron benches formed out of the same metal rods as the trail itself. A worker was standing at the entrace keeping track of how many people were coming in and out.

If you’re cycling, you’re required to walk your bike down the ramp to the mouth of the tunnel. Right from the start, I was deeply impressed by the construction of the walkway. The choice of building materials allows water to fall straight through and into the river below (put your phone somewhere safe, you would not want to drop it here), and the path had been constructed to fit around the trees and the shape of the slope.

At the entrance to the tunnel, I encountered another neat design choice. A triangular pool juts out following the lines of where the old bridge would have been. The water level in the pool is just slightly higher than the level of the path, meaning that the first few metres into the tunnel are flooded. At first, this seems like a terrible design oversight (and time may yet prove that it’s hard to maintain, although I hope not), but this is actually entirely intentional.

The first reason for allowing the entrance to be flooded is that it allows for some stunning pictures. As soon as the tunnel opened, local social media sites were swamped with photos of people posing in the entrance. From the right angle, the water creates a perfect reflection of the arched opening.

The second reason that it was important to let fresh water continue to flow in is that it creates a healthy environment for the creatures living here. Right beside the tunnel mouth, you are closest to the stream, and if you peek into the illuminated waters, you’ll spot a whole host of critters living their lives down there. It’s so cool that you can have this little glimpse into their world.

There are actually two tunnels. The first is only about 110m long, so it never gets fully dark.

There’s a small opening between the two. A couple of staff members (or maybe volunteers) were stationed here.

The second tunnel is the proper Sandiaoling Tunnel, and it is a little gloomier than the first. I visited a few days after the application requirement was lifted, so it was probably a little busier than it will be by the time this is posted. There were enough people walking through that it never felt lonely or spooky. That said, I think even if it does end up being quieter months or years down the line, the design means that it’s unlikely to ever feel too gloomy. The lights are dim, sure, but there also no illuminated spaces that could be hiding anyone. The slatted surface of the trail allows water to drip through without puddling, but after your eyes adjust, it also allows you to see what’s going on below you.

About midway through the longer tunnel, I glanced up and happened to spot a colony of bats hanging out on the roof. They were all motionless during my morning visit, but I imagine that people who visit close to the evening might find themselves accompanied by flying bats.

Another interesting detail was the bright orange stain left by minerals leaching out of the earth and being deposited on the surface of the walls.

The railings vary along the whole length of the tunnel. At times, they’re not more than ankle-height, and at times they’re at waist-height, this splayed design only appeared right as I neared the Mudan-side tunnel mouth.

I happened to glance down at the tunnel floor just before emerging and spotted this busy collection of muntjac prints left in the soft mud.

At the point where you leave the tunnel, the railings morph into benches. I imagine plenty of people probably turn around here and go back the same way.

The bikeway continues past a toilet block and visitor centre (I’m not really sure what purpose this visitor centre serves except for having a map on its external wall). After a while, it becomes just a regular paved road.

I passed under Ruishuang Road just before dipping down into the centre of Mudan.

If you’re not planning on pausing here, you can turn right and head straight on to Shuangxi. But if you’d like to stop for a coffee and a wander, then I suggest you park your bike by the train station first.

I had decided to pause at Mudan Antique Cafe. The cafe is owned and operated by Mr Wu, the son of a Mudan coal mining family. Mr Wu left the town in his teens to seek a better life in the city, but he returned after retiring. Since then, he has established this colourful coffee shop and decorated several of the town’s communal spaces with brilliant murals (the giant blue magpies under the railway bridge are his handiwork). He is obviously a one-of-a-kind creative soul, and is making full use of his retirement. He told me that running the business is something which keeps him energetic and happy, and he enjoys talking to all of the visitors who pass through.

He’s even printed out cute business cards for his establishment that are in the shape of railway ticket stubs.

Once I’d had my coffee, I returned to Mudan Station to pick up another bike and continue my journey onwards in the drizzle towards Shuangxi. I passed through Mudan two or three times while I was walking the Tamsui-Kavalan Trails, and based on my most recent experience, it seems like the town’s popularity has really shot up with the relaxation of Covid regulations and the opening of the tunnel. Even on a grey Thursday morning, it was buzzing with lots of local tourists.

At the far end of Mudan Old Street, take a left turn onto Ruishang Road and follow that the whole way to Shuangxi.

I’d actually walked this way before during my Tamsui-Kavalan Trails journey, and I think these two chaps in the above photo were probably doing something similar. I’d first passed them walking just outside of Houtong, and they’d obviously caught up with me again while I’d stopped for coffee.

Once you hit the outskirts of Shuangxi, take a left turn and head towards the 7-Eleven.

The road takes you across Mudan Creek, one of the two watercourses that give Shuangxi (literally “Double River”) its name.

The YouBike stand is on the right just before you get to the train station. As I was putting mine back in its dock, this rather happy dog trotted past me proudly carrying his lunch.

From here, the station is just another fifty metres or so. I’d just missed a train, so I ended up waiting for about twenty minutes for the next one.

The day had one more treat in store for me though, because as I was waiting on the platform, this happened:

Today’s instalment of the kindness of strangers:
I had almost visited this bakery in Shuangxi, but decided not to, assuming it wouldn’t have anything I could eat. Then, as I’m waiting on the platform, a couple approaches me to offer me this vegetarian green bean pastry. pic.twitter.com/bTNNBAetWM

— Taiwan Trails and Tales (@Taiwan_trails) March 30, 2023

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How to get to Sandiaoling Tunnel

Google Maps address: I started this ride from Ruifang Train Station and finished at Shuangxi Train Station. There are also places to rent YouBikes in Houtong, Mudan, and close to the Houtong-side of the tunnel. I would highly recommend ditching your car or scooter in favour of public transport for this excursion.

Public transport: Catch any local train leaving Taipei bound for Su’ao and alight at either Ruifang or Houtong. Then on the way back, just jump on any northbound train from either Mudan or Shuangxi.

Further reading: There’s a lot out there about this new tunnel. If you’re more into biking than hiking, I recommend this brief write-up of a longer route.

Nearby trails:

• Dacukeng Old Trail
• Menghuan Waterfall
• Sandioaling Waterfall Trail
• Tamsui-Kavalan Trails: Mudan Loop
• Tamsui-Kavalan Trails: Ruifang to Shuangxi
• Youkeng Waterfall

Applying to Visit Sandiaoling Tunnel

It is free to enter the tunnel, but to apply to enter, you’ll need to go via this site.

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Sandiaoling Tunnel Trail Map

GPX file available here on Outdoor Active. (Account needed, but the free one works just fine.)

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