Sandiaoling Historic Tunnel 三貂嶺舊隧道

Historical Background:

The Old Sandiaoling Tunnel, located on the border of Ruifang and Shuangxi districts in New Taipei City, is a former single-track railway tunnel built during the Japanese colonial period and opened in 1922 as part of the Yilan Line. With a main length of 1,852 meters and the nearby 110-meter Sanguazi Tunnel, it served as a vital rail link between Taipei and Yilan for over 60 years before being closed in 1985 following the opening of a newer double-track tunnel. Notable for being one of Taiwan’s earliest railway tunnels excavated using electric rock drills, it holds significant historical, engineering, and cultural value. Designated a New Taipei City historic building in 2019, the tunnel was restored and repurposed as a bicycle route, reopening to the public in July 2022 as part of a broader effort to promote heritage preservation and low-carbon tourism.

The name Sandiaoling comes from the Spanish name Santiago, which was the name the Spanish gave to the nearby Fulong Village and Santiaogo Cape when they landed there in 1626. Sandiao is the Taiwanese transliteration of Santiago.
During the Qing Dynasty, Sandiaoling was also a town along the Danlan Old Trail that connected Taipei to Yilan. 
The Pingxi Line was completed in 1921 by the Japanese for coal transport, and opened to travelers in 1929.

To meet growing transport demand and enable double tracking, construction of the present tunnel began in 1982 and, despite difficult geology and flooding incidents during excavation, it broke through in 1984 and opened in 1985 alongside full double-tracking of the section. The tunnel was electrified as part of the Yilan Line electrification completed in 2000. The Sandiaoling Tunnel is an active railway tunnel on Taiwan Railways’ Yilan Line, located between Sandiaoling Station and Mudan Station in New Taipei City, cutting through the Sandiaoling area of the Jiali Mountain range; the current second-generation tunnel is 2,076 meters long, double-tracked, electrified, and designed for speeds up to 130 km/h.

Hours:

8:30 AM to 4:30 PM (must enter the tunnel before 4 PM), closed Tuesdays

Price:

Free

Online Reservation (Required)

You must create an online reservation using the government website at this link: https://thedarkline.ntpc.gov.tw/index_en.aspx

Rules and Regulations:

• Reservations can only be made a maximum of 14 days in advance.
• Each time slot is for one hour and allows for a reservation of up to 160 people. 
• After making a reservation successfully here https://thedarkline.ntpc.gov.tw/index_en.aspx, please screenshot the successful registration page with the QR code; you will need to show it to enter the tunnel.
• You must enter the tunnel before 4:00 PM.
• Beware that there will be dripping water within the tunnel.
• Be respectful to other visitors and wildlife.

Difficulty:

• Easy
• 3.1 KM one way, which is totally flat
• The whole loop (including taking a train back) takes about 1.5 hours to complete on a bicycle

Where to stay:

We recommend Fullon Hotel which has locations in Tamsui and Fulong near the beach (book on Booking.com here, Tripadvisor here, Agoda here, or Hotels.com here). 
We have stayed at and recommend ​Gold Mountain Ranch, which is a horse ranch and glamping destination in Jinshan. ​You can book a night at Gold Mountain Ranch on Klook here.  You can also check out our full blog on the ranch here. 
We have also stayed at and recommend Hai Xia Your Home which is right in front of Fulong Beach (book on Booking.com here, Tripadvisor here, Agoda here, or Hotels.com here). 

Activities in Taipei:

There are many activities available to enjoy in Taipei such as kayaking, canoeing, snorkeling, SUP / paddle boarding, water biking, and more activities which you can book on Klook here or KKday here. 

How to get there:

There are two entrances:
➡ Entrance #1: Mudan Street, Shuangxi District (Eco-Friendly Tunnel 0K+000)
➡ Entrance #2: Housan Road, Ruifang District (Eco-Friendly Tunnel 3K+192)

By Car/Scooter: From Taipei, take Chengde Road North to Shilin and keep going until it becomes Provincial Highway 2A. The museum will be on your right, hard to miss. There is free scooter parking on the street and paid car parking underground, but it can fill up quickly.
Looking for scooter rental in Taipei? You can search on Klook here or KKday here to search for options. You can also check out our scooter rental guide here. 
If you are looking for car rentals, you can also search Qeeq here, Klook here, or  KKday here. You can also check out our car rental guide here.  
By Taiwan Railway: Take the Taiwan Railway train to either Mudan Station or Sandiaoling Station. The tunnel is a short walk away and can be accessed from either direction. Klook here.
By Bicycle: 
There are Youbike Stations near both Mudan Station and Sandiaoling Station, however there are usually more bikes on the Mudan Station side.
Cycling is the best way to enjoy Taiwan’s landscapes if you have the time and energy. Looking for bicycle rentals in Taiwan? You can use Taiwan’s many Youbike sharing stations, or search for rentals on KKday here, and search for tours on Klook here. You can also check out our Taiwan cycling guide here. You can also book a Sunset Riverside Bike Ride and Historical Tour, 4 Hour Cycling in Taipei, Ultimate 8-Hour Cycling City Tour, or Taipei City Bike Tour with Night Market Experience on TripAdvisor here. 
For more information, check out our Taiwan transportation guide here. 

Map:

Please see below for the location of the Sandiaoling Entrance:

See below for the location of the Mudan entrance:

Drone Footage:

Play

Our Journey:

I have been to the Sandiaoling Tunnel once, but I had taken many trips to Sandiaoling before the tunnel opened to the public. We were able to enter the tunnel at the last possible second, find some of the last Youbikes left at Sandiaoling, and ride with our kids through the tunnel in about half an hour.

I first learned about the tunnel’s opening from the many Instagram posts from influencers showing the mirror pool on the Sandiaoling side. Because of the mirror pool, you will have to walk through water in the tunnel.

We drove a car to Sandiaoling and parked there, but I am going to show you the train route because we had to take the train anyway to get back to our car. The tunnel closed at 4:30 PM, so we could not cross through the tunnel again to get back to Sandiaoling.

From Sandiaoling Station, you will need to walk over to the tunnel. Sandiaoling Station is the only Taiwan Railways station that is not connected to a road.

You have to walk along the sidewalk here to get to the tunnel.

Here you can find some old relics of coal mining’s past in Sandiaoling.

A row of old coal mining-related storehouses or other related buildings.

I am not sure what the use of these buildings was, but now they are all unusable.

Taroko Express / Puyuma train passing by.

Abandoned brick house along the riverbank.

View looking up a small stream.

Map of the area. You have to walk over to Sandiaoling Village, cross the bridge, and then circle back to the tunnel.

TRB related building along the train tracks.

Someone’s house here is only accessible via these steps.

A train from the Pingxi Railway Line rolls in.

First view of the Old Sandiaoling Tunnel from across the river.

Vertical view of the tunnel.

View of the walkway down to the tunnel.

The walkway ends here, and you have to walk under a tunnel under the tracks.

Juguang Train going through the new Sandiaoling Tunnel.

If you brought your own bike on the train, you need to walk it down and up these steps. But there is a little ramp on the side.

The steps inside the tunnel.

View from the other side.

Another view of the new Sandiaoling Tunnel.

We then walked along the sidewalk here.

Some old railway ties near the trail.

Shuoren Elementary School, above, was originally built as a Japanese language school in 1938. It was officially made an elementary school in 1964. Due to a lack of children in the area, it officially closed in 1996. 

Crossing the tracks at Sandiaoling.

Restaurant at Sandiaoling.

View up the Keelung River.

View looking back down the tracks at Sandiaoling.

Some old-style houses at Sandiaoling.

Pingxi Train crossing the bridge at Sandiaoling.

You can then follow the riverpath downriver here.

Aerial view of a train passing through the new Sandiaoling Tunnel here.

3:55 PM, we reached the Youbike Station at Sandiaoling, which had only two bikes left!

We snatched those two bikes and quickly made our way to the old Sandiaoling Tunnel.

Taroko Express is going by.

Map of the area.

Pingxi Railway line passes by.

4:03 PM, we reach the entrance to the tunnel three minutes late, but because we are on bikes, they let us in.

Here we showed them our QR code, which we got by registering online the day of: https://thedarkline.ntpc.gov.tw/index_en.aspx

View of the Keelung River below.

As you can see, the entire trail is made of rebar. I am not sure who made that call, but I am sure this trail will eventually just rust away. Also, do not drop your phone on this trail! It could fall through the cracks and be lost forever.

Local train passing by.

Entrance to the old Sandiaoling Tunnel.

Aerial view from the outside of the tunnel.

Here, you have to walk/ride through the water.

View of the famous mirror pool.

View through the first part of the tunnel.

The first part of the tunnel is rather short and comes to this open area in the forest.

Another nice place to take photos.

i think there are some Chinese characters in the stone here.

Fallen Rocks Between the Tunnels

An old stream bed sits in the 20-meter distance between the Old Sandiaoling and Sanguazi Tunnels. A flood-prevention bypass channel was created in the upper reaches of the stream directly above the Old Sandiaoling Tunnel to divert the flow away. In 2001, Typhoon Nari brought heavy rains, which causedthe Keelung River to overflow its banks. A large amount of rock and silt washed up on the old stream bed in between the two tunnels and even washed into the tunnel. Piles of rocks have been left behind, forming a unique landscape that extends far inside the tunnel.

A Natural Green Wall with Native Species

The bottom of the old riverbed is largely shaded from direct sunlight. Other than the obvious presence of the railways and the tunnels, the vegetation coverage appears untouched and unaffected. Perennially low in light and moisture evaporation, the environment selects for ferns, Urticaceae, and Araceae.

The Great North Cliff displays the plant composition and vertical layered structure of Taiwan’s low-altitude forest, which can be roughly divided into four strata. The canopy level is dominated by trees of the Lauraceae and Fagaceae families. The understory level is shared by medium-sized palms and tree ferns. The shrub level is dominated by shade-tolerant shrubs, ferns, and large herbs. The ground level is mostly creeping ferns and small ferns. Abundant vines vertically cross each layer.

With an area of only 36,000 square kilometers, Taiwan has 34 families of more than 600 species of ferns. It is also the country with the highest density of ferns by area and is sometimes referred to as the “kingdom of ferns.” Among this abundant fern vegetation is a rare living fossil: the Pteridophytes include Lotus Guanyin (Angiopteris yunnanensis). Black Hair Fern (Blechnum orientale), which can reach a height of more than 3 meters. Medium-sized ferns include leaves that can reach more than 2 meters in height. Small ferns include Asplenium antiquum, Diplazium and Kidney Fern (Nephrolepis biserrata, with Nephrolepis cordifolia), and several Adiantum species, all of which are less than 1 meter in height.

Technically, you should walk your bike, not ride, but no one follows that rule and it is not enforced.

View from the second section of the tunnel, which was much wetter and damper.

My lens started to fog up here. 100% humidity.

This section here has handrails.

4:29 PM: 1K 800 meters.

We kept making our way down the tunnel.

Finally, we made our way through the tunnel.

View of the rebar floor that you do not want to drop your keys on.

We rode along to the Mudan rest station.

Sandiaoling Tunnel Bicycle Path
Old Sandiaoling Tunnel

Introduction
The Sandiaoling Tunnel is located in Ruifang District, New Taipei City. It was originally built as part of the Yilan Railway Line, cutting through the Sandiaoling mountain area.
The tunnel is approximately 1,850 meters long
Originally built for railway use
Later abandoned after railway realignment
Reopened in 2022 as a bicycle and pedestrian path
Today, it combines industrial heritage, ecological conservation, and leisure cycling, allowing visitors to experience the historic tunnel environment while enjoying nature.

Timeline
1922 – Sandiaoling–Mudan railway section completed and tunnel opened
1985 – Railway route adjusted; tunnel taken out of service
2020 – Renovation and redevelopment planning
2022 – Opened to the public as a bicycle path

Tunnel Interior Environment
Tunnel Length: 1,850 m
Tunnel Width: 300 cm
Track Bed Height: 2.4 cm (original railway structure remains visible)
Side Walkway Width: 50 cm
The tunnel is dimly lit, cool, and humid, preserving its original atmosphere. Visitors can clearly see the tunnel’s internal structure.

Space Usage Rules
Motor vehicles are prohibited
Bicycles and pedestrians must share the path safely
Ride slowly and yield to pedestrians
No smoking
No littering
No damage to plants, animals, or historic structures
Keep noise to a minimum
Children must be supervised
Follow all posted safety and traffic regulations
The path is accessible to strollers and wheelchairs, but caution is advised

“Treasure Hunt” – Things to Look For
Cyathea (Tree Ferns)
A native Taiwanese plant is often called a “living fossil.” Thrives in moist, shaded environments.
Bird’s Nest Fern
Common along tunnel entrances and forested sections, growing in cool, damp areas.
Fireflies & Butterflies
The area is home to fireflies and butterflies, especially visible during certain seasons.
Bats
The tunnel provides an important habitat for bats. Please do not disturb them.

Route Map & Points of Interest

Sandiaoling Tunnel Bicycle Path – Five-Senses Experience

Route Overview

This map shows the Sandiaoling Tunnel Bicycle Path, following the route of the former railway tunnels. The path connects multiple scenic, ecological, and historical points along the old railway corridor.

The route includes:

• Starting point near Mudan Station
• Old railway tunnels, platforms, and bridges
• Ecological observation areas
• Rest stops and viewing platforms
• Ending point near Sandiaoling Station

Distances are marked along the route, showing kilometer points from start to end.

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Key Stops Along the Route (Selected Highlights)

1. Mudan Station
   Opened in 1922 during the Japanese era. The station played an important role in coal transportation and local development.
2. Mudan Old Street
   A historic settlement area reflecting the daily life of early railway and mining communities.
3. Rest Area
   A shaded stop for cyclists and pedestrians.
4. Tunnel Section (Third Sandiaoling Tunnel)
   One of the main attractions of the route, offering a cool, atmospheric ride through the historic tunnel.
5. Railway Track Remains
   Preserved railway sleepers and tracks demonstrate early railway construction techniques.
6. Rock Wall & Geological Section
   Exposed rock layers reveal the geological structure of the area.
7. Bridge & Valley Viewpoint
   Offers views of the surrounding forest and river valley.
8. Ecological Observation Area
   Habitat for various insects, plants, and small animals.
9. Stone Platform Remains
   Former railway platforms still visible along the route.
10. Old Tunnel Entrance
    Shows the original tunnel construction and drainage design.
11. Water Channel
    Historic drainage facilities used to protect the railway from flooding.
12. Railway Machinery Base
    Area where maintenance and railway equipment were once located.
13. Sandiaoling Coal Transport Facilities
    Evidence of coal-loading infrastructure from the mining era.
14. Historic Walkway
    A preserved pedestrian route once used by railway workers.
15. Sandiaoling Station
    The endpoint of the route and a key historic railway hub.

4:44 PM, we reached the Mudan Rest Station a few minutes late, which meant the employees were late getting off work. Sorry!

Next, we continued on to Mudan Station.

Local train passing by.

We continued on this one-lane road.

I cannot stop myself from taking photos of bananas.

View further down the path.

You can also visit the old Longmei Mine from here.

The Shuangxi Sports Park is also here, which is a large grassy park you can check out.

We then crossed under this bridge.

This is the steepest hill on the loop. I recommend getting off your bike to go up and down.

Mudan Old Street 牡丹老街

Mudan Old Street is a small old street in the Mudan Neighborhood of Shuangxi District. The old street is almost totally a residential area. Now it is a quiet town with very few tourists, but with lots of natural sights, mountain roads, camp sites, and hiking trails nearby…(read more)

View up the Shuangxi River here.

As you move toward Mudan Station, you can see a lot of artsy displays here.

More artwork along this street.

2024 Year of the Dragon.

Another art shop that was closed when we visited.

This shop usually sells rock flower jelly.

Year of the Dragon decor.

As you can see, there are way more Youbike Stations here in front of Mudan Station. Therefore, I recommend taking off from here instead.

View of the front of the station.

You can also go biking and explore more around Mudan.

View of the platform at Mudan Station.

Train tracks at Mudan.

View down the tracks at Mudan.

An express train passes by.

We then put our bikes on the train to get back to Sandiaoling where our car was parked.

5:18 PM: We made it back to Sandiaoling Station.

Thanks for reading, and stay tuned for more blog posts to come.

Check out our guide to the Pingxi Railway line here.

Check out our guide to Taipei here.

Check out our Taiwan cycling guide here.

Check out our full guide to Taiwan here.