Exploring Abernant (Merthyr) Tunnel


Recently, with my good friend Sparhawk (www.blackmountainsite.co.uk), I made a visit to Abernant Tunnel near Merthyr.  We found the tunnel on an OS map, took a brief glance at it’s eastern end and decided to come back and take a look a week or so later.

East Portal

East Portal

Mainly due to geocaching, and the subesquent visit a while back to the Tidenham tunnel in the Wye Valley (now sadly blocked by a new fence), to pick up a cache (here), I have discovered a new interest in visiting the abandoned railway tunnels and other industrial sites around the area.  There’s something fascinating about visiting the long-abandoned relics of the industrial age, especially, like in this case, when they are 2497 yards (about 1.5 miles) long and up to 200m below the surface of the hill!

We started off from Gethin Woodland picnic site, we walked about half to three-quarters of a mile (I’d estimate) to the easternmost portal of the tunnel.  This is situated at the end of a cutting I think about 1/2 mile long).  The portal itself is actually fenced off, but the fence has been damaged sometime in the past on the right hand side, so there is easy access.  Before I go any further, I do not condone putting yourself at risk, and it important that you understand that if you do decide to explore locations such as these, you do so at your own risk.  You should NOT do it alone, and you make sure you take adequate lighting (with replacement power) and wear suitable footwear.  These sorts of places can be very dangerous if you act like a fool and don’t treat them with the respect they deserve.  DON’T take unnecessary risks, and make sure somebody knows you are going, and where you are going.  Finally, you should never, ever, ever, commit any kind of damage to get into these places, or once inside (including graffitti).  Doing so is criminal damage. Remember, take only photos, leave only footprints.  If you can’t get in, then hard luck.

Anyway – lecture over.

A brief bit of history first.  Abernant Tunnel (also known as Merthyr Tunnel) formed part of the old route from Merthyr to Neath.  The last train passed through the tunnel in 1962 (29th December to be precise!), and the tunnel was blocked up in 1967.  In 1998, the walls were removed and replaced with fencing.  This tunnel is 2497 yards long, making it the second longest in Wales.  The longest is the Rhondda Tunnel, at 3443 yards, but this is now inaccessible, having been buried and re-landscaped at both ends (strictly speaking it IS accessible, but only via a drainage shaft, and not without the massive risk of dying of gas poisoning due to it being adjacent to a coal deposit).  Therefore, Abernant is now the longest still-accessible tunnel in Wales.  For a nice pic of the tunnel with the last train going through it in 1962, go to www.alangeorge.co.uk/merthyrtunnel.htm.  A more full history of the Abernant Tunnel can be found here.

We arrived and entered the tunnel through the already broken fencing.  On checking it out, the structure looked fairly sound, with much less in the way of visible deterioration than we expected.

The Team

The Team

We carried with us much in the way of torches and headlights, meaning that at no time did we have a lack of light.  This is something which is vital, and its importance should not be underestimated.  The tunnel itself is S-Shaped, which means that you cannot see either end of the tunnel from the central mile.  This means BLACK.  and I mean PITCH black.  The first part (20yds or so) of the tunnel is flooded, but this is only to about 3-4 inches, and is no problem to wade through with walking boots.   The floor is covered in the normal aggregate that you find on railway lines, and there is no longer any sign of the tracks or sleepers, so the tunnel looks like it may have been re-floored since closing.  The tunnel itself was mostly brick-lined in the sections we saw.  However, it is apparently much wider at the western end, and isn’t totally lined.  We’re yet to see this however.

This time, we only went to the 89CH mark in the tunnel.  This means 84 Chains, which is approx 1.7km.  I calculated that the tunnel is 2.28km long, and a chain is 20.11m.  Therefore, we went 2.28km – (84*20.11) = Approximately 590m into the tunnel.  This was far enough that we could no longer see the eastern portal by which we entered.  We decided today not to go any further today, but may return in future to see a bit more.

During our visit, we took some pictures, which you can see in the gallery below, and did a bit of light painting with our torches, by setting the camera to a 30 sec exposure, and walking up the tunnel waving our torches about. Feel a bit silly doing this, but it produces some interesting results!

All-in-all, this was a very interesting visit.  Again, visiting these places is entirely at your own risk, and it is good to read up about the risks before you attempt it. It is, however, extremely interesting, as you get to see a fantastic relics of a byegone age.  For more information about these sorts of places, and how to visit them as safely as possible, visit www.darkplaces.co.uk.  If you do decide to do it, whatever you do, use your best judgement, and be careful!

Enjoy the full range of pics…

88 Responses to “Exploring Abernant (Merthyr) Tunnel”

  1. mark owen says:

    went up to the merthyr end today and the fence has been repaired and fresh anti climb paint

  2. mark owen says:

    went up to the merthyr end today and the fence has been repaired and fresh anti climb paint lets hope someone finds a way in soon.

  3. richard says:

    thats a shame. kids today are hopeless. When we were lads we would have battered, prised, dug our way through in no time

  4. blaencwma says:

    just to let you all know the rhondda tunnell is accesible,and yes by the drainage shaft,there is no gas,oxygen a liitle low,i go down there every sunday,i just cant keep from there

  5. les says:

    myself and 2 mates walked the entire lenth from cwmbach side thro to merther side then over the top following the pipeline in 1986 without any torches with just the glow of my trainers hitech nitelights member them ha must have been crazy

  6. les says:

    great site axeman ime due a trip down the abernant tunnel when i get a day off ile let u now how it goes what a engineering masterpiece

  7. Steve says:

    Reading your article regarding Merthyr Tunnel brought back a vivid memory of when 4 of my firends and myself walked its entire length (1.5 miles you say??), starting from the Merthyr side. At the time of our adventure (in about 1980) the Merthyr entrance was walled up as you mentioned in your report. However, it was still accessible via a small doorway-sized aparture.

    I recall the experience of being totally engulfed by the dark, as once we lost the light from the Merthyr end, we switched off our torches – we were all determned not to be the first to “chicken out” and switch a torch on, so as you can imagine, we remained in the inky blackness for what seemed like an eternity! I have no recollection of the condition of the Aberdare entrance, but do remember we took an overground route back to Merthyr, as several phone calls we made (via a fixed line in a red phone box, of course) failed to persuade a parent to drive over the mountain to collect us!!

  8. Axeman says:

    Its fantastic to hear everyones’ stories of the tunnel. I love that it’s obviously been providing people with a lot of good memories for quite a few years now. Hopefully it’ll carry on doing so for a good time yet…

  9. AintBigAintClever says:

    Went through today armed with floodlights and a camcorder! Tunnel is still accessible from the Aberdare side (someone’s taken an angle grinder to the fence) but Merthyr end is locked shut, so if you’re going right through, make sure you’ve got 3 miles’ worth of battery power ‘cos you’re going back the same way!
    Video will be on YouTube once I’ve edited it.

    Interestingly, the Merhyr-side “room” (about half a mile in) now appears to be a Mormon chapel, all painted up with a bible in the little alcove and tealights everywhere. Weird.

  10. Owen says:

    I live in merthyr, I’ve been to the merthyr end of the tunnel but couldn’t really be bothered to try and scale the shiny new metal fencing thats now blocking the entrance. anyway, the point is that Sustrans and the welsh assembly is desperate to get hold of this tunnel and the trackbed as potential pedestrian/cyclist route from Aberdare to Merthyr. its only in the consultation stage at the moment and would obviously take serious investment but its something I’d like to see. merthyr to aberdare in about 10 minutes by bike! I live in the Pant area of merthyr, right slap bang next to the old merthyr/brecon line, part of which is now in the hands of sustrans and is now possible to get from pant down to merthyr common (where the old dowlais top station is) thanks to a new footbridge. Sustrans do a good job, while they are not reopening closed lines they are at least ensuring that the track beds remain extant in case such a thing should ever be possible.

  11. Gareth Davies says:

    I can just remember tunnel open. My father used to have a night out in Merthyr and if last bus missed he used to walk home to Trecynon through the tunnel. Be aware of closed tunnels because of the likelihood there may be a build up of gas which could be deadly, especially talking to an old miner and the Black Damp gas which takes the oxygen out of the air. I thought the floor of the tunnel had collapsed many years ago!!!

  12. adrian says:

    jan 21 went to the tunnel today both ends are open took same photos putting them on alan george.co.uk

  13. cunningcorgi says:


    Merthyr portal now open and accessable (the gate has been angle grinded in two places so no climbing or crawling !).

    Abernant portal fully open as per 04/09/11. The angle grinders work has yet to be repaired.

  14. Wonky says:

    Bad news about the Merthyr portal I’m afraid. Went the today 27/2/12 and it’s been repaired. I had planned to walk all the way through with my dogs and a friend, but no good. This time they’ve welded solid sheet steel over the frame of the old fence and put a very sturdy lock on it. I believe this was done on friday 24/1/12 as that date is finger painted on the steel (damn! only missed it by 3 or 4 days). I would have climbed over but for my three dogs not liking heights!!! I went up the beacons then and walked the Torpantau tunnel and then the Miler, just to feed my tunnel walking urges. Shame though. I don’t know about the Aberdare end, but if anyone could post any info on this it would come in handy. Still would love to walk this tunnel. Great site by the way Axeman.

  15. cunningcorgi says:

    You’re wrong on the date there Wonky. We went through (Abernant – Merthyr – Abernant) on Sunday 19th February 2012. There was grafitti in the platers cabin from 29th January 2012 also evident.

    The gates must have been repaired sometime after 20th February 2012.

  16. pentre man says:

    this is a message for blaencwma I just live down the road from you and If you a willing for me to come down with you and I would love to see it please message me on rossmorgan2010@hotmail.com and I would love to talk with you about the trip down the rhondda tunnel. Many thanks.

  17. Wonky says:

    Damn. Typed the wrong date there. The plates went on 24/2/12 not the 24/1/12 (teach me to have a drink and try and type!!). Still on my list of tunnels to go through.

  18. Les says:

    Just looked at the excellant video of abernant tunnel
    On u tube by aintbigaintclever superb good work !
    Still aint had time to get down ther myself see u soon x

  19. Les says:

    That morman chapple inside thats wierd good tho

  20. Dai says:

    blaencwma <<< Hiya mate, i deffo fancy a trip down the Rhonda tunnel mate,maybe you could show me one day :)

  21. gavisgon says:

    no gas deff down blaencwm tunnel,was in there bout a 2 months ago walk the length of it wat a amazing experience

  22. pentre man says:

    HI gav how do you get down there. Prahaps wr could meet up in blaencwm and you could take me down there and show me. I always wanted to see what it is like. If yes what is ur email address.

  23. puppet1973 says:

    Went to both ends of the Abernant tunnel today (7/9/12) – Merthyr and Cwmbach – and both are still inaccessable. Plated fences, combi locks and anti climb paint on BOTH portals. If anyone finds them breached in the coming months be sure to post on here!

  24. cunningcorgi says:

    You can still get in at the Merthyr end with a bit of thinking outside the box (we did in June).

    Email me at seanie007@hotmail.com for a bit of advice if you want. Abernant end is basically a no go atm…

  25. puppet1973 says:

    Ladder? Ha ha! Visited Gellifelen and Clydach tunnels yesterday. The two conduits in the Gellifelen tunnel that link the northern to the southern bore is still fenced over, although one is easily navigated. The Clydach tunnel still has the conduit that links the two and this is not fenced. The bricked up bore (southern?) is accessable through here, although the ceiling at the bricked up end looks suspect and we decided not to walk under it (broken support beams).
    Went to the Morlais tunnel again today which is an old friend as i’ve been visiting it since I was 7 (1980). However, the Abernant tunnel is still calling me!

  26. cunningcorgi says:

    The ‘fencing’ in Gellifelen is easily negotiated. Buster Bloodvessel would have no problems getting through it ! Might have a bit of a squeeze afterwards though.

    Is Clydach now open ? Both the non bricked bore ends had the pallastine fencing when we were there this year, not that this was a problem. Didn’t notice too much wrong with the ceiling and the bracing seemed to be pretty stable.

    Assume the first pepper pot in Morlais is still spewing water in ? Never seen it dry at this point.

  27. puppet1973 says:

    Yes, the left hand tunnel, north I think, has fencing, but one slat is missing and bent open slightly. The right hand bore is secure, but someone has dug a little under the fence. If you were small enough and didn’t mind getting dirty then I guess you could crawl under. Like I said, the left hand one has its fence breached so its easier just to go through here and use the conduit to explore the other tunnel. The bracing had fallen timber on the floor, so I didn’t risk going under just in case as we were right at the end anyway.

    The first pepperpot from the Pontsarn end is still very wet! It’s still a great tunnel, impressive size and moderate length – but you know that! I’ll definately drop you an email to swap tips. The Abernant still draws me in. As far as I can tell, it’s still the longest “accessable” tunnel in South Wales that hasn’t been completely landfilled.

  28. puppet1973 says:

    Still no breach at the Merthyr end of the Abernant tunnel. Some evidence of a crude abseil into the portal from above remains from a recent explorer!

  29. cunningcorgi says:

    puppet – when you visited Gellifelen in September, was there new fencing on the right hand bore (as you come from Clydach) ?

    There is fencing on it now. Not very good fencing that dosen’t do its job but fencing none the less. Some interesting new signs on the cross-cuts in the tunnel too.

  30. Richard Jones says:

    Hi Axeman, great site. My family on my Father’s side are from Merthyr and we used to regularly walk through the Aberdare tunnel. I recently (October) took a trip down memory lane (after at least 35 years!) and spent a couple of days in Merthyr, it took me a while but I eventually managed to find the eastern portal of the tunnel, unfortunately it is currently well sealed up, (welded steel gates, anti climb paint, etc,etc) but who knows, there are lots of people out there that carry portable anglegrinders and crowbars so it may one day be possible to walk it again – lets hope so.


  31. puppet1973 says:

    Yes there was fencing, but two slats were missing.

  32. nathan says:

    i am planning to go down there some weekend with some friends do u know if both ends are open? my father done it when he 13 with no light and went back over the mountain

  33. cunningcorgi says:

    Both portals completly closed off at the moment with bigger gates and litres of engine grease smeared all over them.

    Residuary are also in the tunnel as we speak (26th January 2013) carrying out the 5 yearly comprehensive inspection (they dragged all their gear in through the Abernant portal). Word is that they will be doing some concrete spraying in the tunnel although I find this very hard to believe as the tunnel was in excellent condition the last time we went through in June 2012.

  34. very good web site takes me back many a year walked the Aberdare tunnel as a boy with my mates mike Collins jeff fitsgerald mike powell and idris hamer. many time,s the train was coming and dived for cover we walked in the dark fell over the sleepers and frighten the shit out of each other good old days keep up the good work colin thompson

  35. guitar man says:

    I live a few 100 yrd from tunnel in cwmbach we used to walk the tunnel with my mates in the 60s no torches just holding stickes against the wall done it dozens of times great times

  36. jasp78 says:

    Anyone know what they are currently doing in the tunnel? Today I cycled up the old trackbed from llwydcoed, from the old Abernant station there are warning signs about construction traffic, the last section of trackbed up to the portal is completely fenced off with signs prohibiting access. I followed the path which takes you up over the portal and there was a generator and some heavy machinery lying just in front of tunnel entrance. Anyone know what they are doing?

  37. les says:

    Hi all
    Eventually had Time to get down to the cwmbach tunnel today and as I approach the tunnel a van was parked at the entrance of the cwmbach side entrance it was a contract firm named Hammond so I got talking to the gent in the van who is on walkie talkies with the boys inside
    He told me there is a lot of structural work going on in there as the metal band’s abduction brickwork is rotting as I am a engineer who have a tunneling experience working with barhales tunneling they have concrete spraying a couple hundred meters here and there basically as they don’t want the tunnel collapses cos of farm’s basically on top suffering subsidence .
    I will call down there in the autumn to keep u all informed take care x

  38. les says:

    Hi again ! Forget to mention they ad to evict a tramp who was living in there bloody recession init takes the best of us pity .

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