The Dduallt spiral
The track loops over itself in a full circle to gain height, the only such spiral on a public railway in Britain.
Unknown authorUnknown author — Public domain · ARG_Flickr — CC BY 2.0 · SchmalspurDVZO — CC BY-SA 4.0 · SchmalspurDVZO — CC BY-SA 4.0
This is the oldest surviving railway company in the world. The line opened in April 1836 to bring slate down from the quarries at Blaenau Ffestiniog to the harbour at Porthmadog, and for decades the loaded wagons rolled down by gravity alone while horses hauled the empties back up. Today a steam locomotive does the work on a track barely sixty centimetres wide, climbing more than 200 metres over roughly 22 km through the Vale of Ffestiniog, from a sea estuary to a town cut out of grey stone. The journey is the destination, not what waits at the end of it. The train leaves Porthmadog across the long Cob embankment over the estuary, then enters oak woods and threads between lakes until, at Dduallt, the track loops over itself in a full spiral to gain height, the only such spiral on a public railway in Britain. The twin-chimney Double Fairlie locomotives are this line's own design and you will scarcely see them working anywhere else. The main Mountain Spirit service takes an hour and a quarter up, allows around fifty minutes in Blaenau Ffestiniog, then returns, so budget a little over three hours. An adult pays £49.75; a child aged 3 to 15 pays a flat £5, which makes it an excellent deal for large families. Booking online adds a 6% fee, so the counter price on the day is the cheaper one if seats are left. A frank tip: if the scenery matters more to you than reaching Blaenau, the shorter Woodland Wanderer to Tan-y-Bwlch at £29 gives you the prettiest stretch of the valley plus an hour's break at a woodland station with a tea room, a trail towards Llyn Mair and a children's play area, and saves two adults around £40. Blaenau Ffestiniog itself is a slightly bleak industrial town in the rain; its main draw is the Zip World adventure site in the Llechwedd quarry. Seats are snug, folding pushchairs go beside your seat while space for a large pram in the guard's carriage is limited, the cafe and shop at Porthmadog are decent, and dogs travel on a £5 ticket. Booking ahead is always wise and close to essential in July and August. Porthmadog sits on the south-western edge of Snowdonia, about 20 minutes by car from Beddgelert on the A4085 and about 45 minutes from Betws-y-Coed on the A470 through Blaenau Ffestiniog. The station car park is reserved for Blue Badge holders, but a fenced section at the top of the neighbouring Llyn Bach car park is free for passengers, open 07:30 to 20:00 on a first-come basis, a short walk from the platform. Services start on 21 March 2026 on selected dates, then run daily from April until 31 October, and stop until the Santa trains in December; outside that window there is nothing to see but a locked station.
The track loops over itself in a full circle to gain height, the only such spiral on a public railway in Britain.
Twin-chimney, back-to-back steam engines born on this line and scarcely seen at work anywhere else.
The first minutes cross a long embankment built a quarter-century before the railway, over the Glaslyn estuary, with the Snowdonia peaks filling the window.
Harbour Station, Porthmadog LL49 9NF
They are different experiences: Snowdon takes you to the summit of the highest peak in Wales, its steam ticket runs above £60 for an adult with children from £35, and it sells out weeks ahead. Ffestiniog is a longer ride through woods and lakes and a child pays £5. If you have one outing and clear skies, choose Snowdon; with young children or a cloudy day, Ffestiniog is the safer bet.
Yes, with a caveat: one-way tickets are standard class only and are sold at the station on the day rather than pre-booked, so they depend on space. If you are planning this at the height of summer, keep a fallback, or take the shorter Tan-y-Bwlch return instead.