Roni Size Plays the World's Deepest Rave in a Welsh Mine

Roni Size will play a one-off set on Thursday, October 15, 2026 inside the abandoned Cwmorthin slate mine in Eryri (Snowdonia), North Wales, at a chamber the organisers put 1,375 feet (about 419 metres) below ground. The event is run by Casio's G-SHOCK brand as the launch of its new MUDMAN GDG-B100 watch, and it is billed as the world's deepest underground rave. Entry was by ballot only, the ballot closed on October 9, 2026, and only "a handful" of places exist. Everyone else gets it via G-SHOCK Radio, with the full set promised afterwards.

That is the headline. The more interesting questions sit underneath it: who is paying for a drum and bass rave in a Welsh mountain, what "deepest" actually means when the Guinness concert record sits at roughly 2,700 metres, and what a ballot-only party for a few fit strangers says about where rave culture is in 2026. We read the organiser's own page, the press coverage that followed, and the sources on the mine, and we flag below everything we could not confirm.

What is the world's deepest rave with Roni Size?

It is a one-off "G-SHOCK Sessions with Roni Size" in a slate mine, with attendees reaching the dancefloor by descending dark tunnels and waterlogged passages, crossing underground ravines, riding zip lines and abseiling down rock faces. That is the organiser's own wording on G-SHOCK's UK MUDMAN page, which gives the date as October 15, 2026, marked "AM + PM", and the venue as Cwmorthin Slate Mine, Eryri, North Wales.

MusicRadar and Mixmag both ran the story in the first week of October, and Mixmag cites a press release as its source. The music is only half the pitch. The other half is a "specialist sound experiment": vibration transducers drive parts of Size's set into the slate, while geophones and hydrophones record how the frequencies travel through rock, mud and water. That recorded response is then fed back into the live mix.

What are the verified details?

The "free" detail comes from Time Out, which also describes the dancefloor as the deepest accessible point in the UK. The G-SHOCK page we read does not state a price, so treat "free" as reported rather than organiser-confirmed. The Go Below involvement, the Starlink link and the Mixcloud upload come from WeRaveYou, which dates its report October 7, 2026, and Nation.Cymru, which published on October 6, 2026. Both read like a shared press release, so they are one source, not two.

What could we not confirm?

Quite a lot, and it matters. No other performers are named in anything we read: the only other names in the MusicRadar piece are Fabio and Grooverider, and they are billed for a separate 2027 Bristol show. We found no published age, fitness or equipment criteria, only a statement that winners must meet them. We found no capacity figure beyond "a handful", no accessibility statement, no safety plan, no licensing details and no named record-keeping body. T3 and Time Out do not describe a formal record application at all, while Nation.Cymru says evidence will be submitted for "independent recognition" without saying to whom. Nation.Cymru's headline also says 1,400 feet while its body says 1,375, which looks like rounding. The organiser's figure is 1,375.

One more wrinkle: the G-SHOCK page lists "AM + PM" while the press coverage talks about a live broadcast "on the night". Underground there is no night, so it is possible the descent runs in sessions. Nothing we read explains this, so we are not guessing.

Where is Cwmorthin, and why does a slate mine matter?

Cwmorthin is a former slate quarry and mine west of Tanygrisiau, near Blaenau Ffestiniog in Gwynedd. According to Wikipedia's entry on the quarry, the Casson family opened it in 1810, the Cwmorthin Slate Company formed in January 1861, and the neighbouring Oakeley quarry took it over around 1900. Oakeley closed in 1970, there was small-scale working in the 1980s and 1990s, and all work reportedly ceased in 1997. Sources disagree here: Sub Brit says it stopped working as a separate quarry around 1939 and was afterwards reached through Oakeley. Both can be true, because one describes the independent quarry and the other the wider working life of the mine.

The bigger context is the slate itself. The Slate Landscape of Northwest Wales became a UNESCO World Heritage Site in 2021, and Wikipedia records that Wales produced 92 percent of UK slate in 1882, that output peaked in 1898 at over half a million tons with about 17,000 men employed, and that the Oakeley mine at Blaenau Ffestiniog was the largest slate mine in the world. Blaenau's slate was worked underground rather than in open pits, and the parish population rose from 732 in 1801 to 11,274 in 1881. So the drop into the dark is not a stunt location pulled from nowhere. It is a working landscape that built a town, and this is one more use for the chambers its miners left behind.

The same mine already sells a different kind of descent. Go Below runs Deep Sleep, an overnight stay in cabins at 1,375 feet that Wikipedia describes as opening in April 2023, with guests given a helmet, light, harness and boots. That is the same depth figure the rave uses. We are not claiming it is the same chamber, only that the number is the operator's established selling point rather than a fresh measurement made for the party.

Who is Roni Size?

Roni Size, born Ryan Owen Granville Williams in Bristol on October 29, 1969, is one of the founding figures of drum and bass. According to Wikipedia, he was expelled from school at 16, went to house parties thrown by the Wild Bunch sound system and learned production in a basement project, and with Krust, DJ Suv and DJ Die he founded the Full Cycle label.

His breakthrough was Roni Size and Reprazent. The group made its live debut in April 1997 at Tribal Gathering, and its debut album New Forms came out on June 23, 1997 on Talkin' Loud. That record won the 1997 Mercury Prize. "Brown Paper Bag", with vocalist Onallee, was one of its singles. Later albums included In the Møde in 2000 and a solo record, Touching Down, in 2002. Reprazent were revived in 2008 with New Forms², and Wikipedia notes Coachella and Ultra appearances in 2009.

How he works matters to this story. In a 2018 Mixmag piece, which originally ran in the Guardian, he describes going to raves and recreating the parts he liked when building his own music. In MusicRadar's report he talks about "happy accidents" such as playing a track at the wrong speed, and says Bristol raves happened "down in tunnels" and on front lawns. Playing to the room is the point of his whole approach, so a room made of slate is at least consistent.

He is also not retiring into novelty gigs. MusicRadar reports that he has announced an outdoor show at Bristol's Lloyds Amphitheatre on June 25, 2027, marking thirty years of New Forms, with Fabio and Grooverider supporting. For more drum and bass context on this site, see our report on Noisia's reunion.

Is a rave underground a new idea?

No. Parties in caves, quarries and disused industrial buildings are as old as the rave itself, and what has changed is who foots the bill. Here is what we can source.

What were the Coniston cave raves?

The best documented British precedent is also a slate quarry. According to VICE's 2018 feature, Outhouse Promotions, later the "Cave Crew", threw parties in a cave at a remote slate quarry near Coniston in the Lake District from the late 1980s into the early 1990s. Organiser Dave "Steely D" Steel recalls them growing from about a dozen people to thousands, with house, acid, Belgian techno and Detroit records on the decks, and police roadblocks backing traffic up for miles. The Vane gallery's note on Matt Stokes adds that word of mouth drew crowds from across the UK in summer 1991, that the landowner had the cave entrances drilled for blasting as a last resort, and that the Cave Crew had disbanded by 1993 after equipment was confiscated.

The parallel is useful and the contrast sharp. In Coniston the cave was the venue and the police were the problem. In Cwmorthin the mine is the venue and a watch brand is the permission slip.

How deep have gigs actually gone?

Here "deepest" needs care, because it depends what is being measured. The Guinness record for the deepest underground concert has changed hands more than once, and the figures are not measured the same way.

The sources are Euronews, Guinness World Records and CBC. Note the Guinness figure is below sea level, while the Cwmorthin figure is described as below ground level, so the numbers are not strictly comparable. Even so, the order of magnitude is clear: the concert record is several times deeper than the Welsh mine. So "deepest rave" is a narrow category claim, not a depth record in the usual sense. We have not found any prior "deepest rave" record to beat, and the organisers have not named one.

What about other reused spaces?

Rave has always colonised buildings that were built for something else. The Pula fortress that first hosted Dimensions Festival was a mid-19th-century military site, and London's Printworks was a print works. Those venues were turned into clubs by promoters over years. What is different about Cwmorthin is the one-night, brand-built, broadcast-first format.

How do you get in, and is it safe?

The ballot closed on October 9, 2026 at 15:00 GMT, so you cannot apply now. If you were not picked, the practical route is G-SHOCK Radio on the night and Mixcloud afterwards. We have not seen a G-SHOCK Radio link for the broadcast.

On safety, the facts are thin and we will not pad them. The route involves stairs, waterlogged passages, zip lines and abseils, and the organisers say winners must meet age, fitness, clothing and equipment requirements without publishing the detail. Go Below's own site lists its Hero Xtreme trip at ages 14 and over and claims experienced guides, though it does not describe qualifications. Secret GB points out that a 2023 report on Deep Sleep, a different trip, describes about 45 minutes of uphill walking and then roughly an hour underground, so this is not a casual door-to-dancefloor evening.

On law, the rave provisions of the Criminal Justice and Public Order Act 1994 were a response to the Castlemorton free festival of 1992, but section 63 as written covers gatherings on land in the open air of 20 or more people, with amplified music at night, so it is not the obvious framework for a managed underground event, and it exempts licensed activity under the Licensing Act 2003. What licence, if any, applies underground in Cwmorthin has not been published, and we are not offering a legal opinion. Our existing report on why the UK keeps losing its nightclubs explains how restrictive the UK's licensed-venue landscape has become, which is part of why a brand-run one-off in a mountain is attractive in the first place.

Accessibility is the clearest gap. We found no statement from the organisers on access for disabled people, and the route as described suggests it would be demanding for many. That should be said plainly, not buried.

What we make of it

This section is RTS.FM's own opinion, not reporting. Each point comes with the strongest argument against it.

1. It is a product launch first and a rave second. The G-SHOCK page frames the whole thing as the launch of the MUDMAN, and press reports say attendees get the watch before its wider release. The rave is the advertisement. That does not make it fake, but it explains the shape: tiny capacity, maximum spectacle, broadcast as the real deliverable. The counter: brand money is exactly what pays for the transducers, Starlink uplink and guides, and an artist like Size gets to try an acoustic experiment that no club would ever fund.

2. "Deepest" is the weakest part of the pitch and the least important. As the table above shows, the concert record is far deeper, and 1,375 feet is also the operator's long-standing figure for its hotel. The honest framing is "deep for a rave, in a mine the public can reach", which is still extraordinary. Leaning on a superlative that is unverified invites exactly this scrutiny. The counter: we found no earlier "deepest rave" claim to beat, so a category claim is a legitimate hook; organisers say they will submit it for independent verification, and until a body rules, scepticism is a courtesy, not an accusation.

3. The sound experiment is the one genuinely new idea. Pumping a drum and bass set into slate and feeding the rock's response back into the mix treats the mountain as an instrument, which fits the happy-accidents instinct Size describes. Bass-heavy music in a mountain of waterlogged passages is at least a sound worth hearing, and it ties to the wider trend we covered in why festivals now book hi-fi sound systems: sound as the headline act. The counter: nobody outside the mountain has heard the result yet, and a live mix passed through geophones and a satellite link may end up as a good story and a mediocre listen.

4. Access and safety are the real conversation. Rave history is full of people turning up to unlikely places, from the Coniston cave to disused factories, and police stopping them. Here the state has been replaced by a ballot and a risk assessment, which is arguably safer, but also means a handful of fit winners are chosen by a brand. We would like to see capacity, accessibility and safety arrangements published, not implied. The counter: an experienced operator running a controlled descent is exactly how an underground party should be run, and publishing every safety detail for a handful of attendees may simply not have been a priority.

Frequently Asked Questions

When is the Roni Size deepest rave?

It takes place on Thursday, October 15, 2026. The organiser's page lists the date as AM and PM, and does not explain whether that means separate sessions.

Where is the rave taking place?

It is inside the abandoned Cwmorthin slate mine in Eryri (Snowdonia), North Wales, near Blaenau Ffestiniog in Gwynedd. The mine is west of the village of Tanygrisiau.

How deep underground is the rave?

The organisers say 1,375 feet below ground, which is about 419 metres. One news site rounded this up to 1,400 feet in its headline, but the organiser figure is 1,375.

Who is organising the event?

G-SHOCK, the watch brand of Casio, is organising it as the launch of its MUDMAN GDG-B100 watch. Press reports name the adventure operator Go Below as the guide for the descent.

Can I still get a ticket?

No. Entry was by ballot on the G-SHOCK website, and the ballot closed on October 9, 2026 at 15:00 GMT. The organisers say only a handful of places are available.

How much does it cost?

Time Out reports that it is free, with entry by ballot only. The organiser page we read does not state a price, so the free claim is reported rather than confirmed.

Can I watch or listen if I am not there?

Yes. The set is due to be broadcast on G-SHOCK Radio, reportedly via Starlink from the mine, and the full performance is promised on Mixcloud afterwards. We have not seen a published broadcast link.

Is it an official world record?

Not yet. The organisers plan to submit it for independent verification, but no recognising body has been named in the coverage we read. The Guinness record for the deepest underground concert is a separate and much deeper category.

Who else is playing?

No other performers are named in the coverage or on the organiser page we read. Fabio and Grooverider are mentioned only as support for Roni Size's Bristol show on June 25, 2027.

What is the sound experiment?

Vibration transducers send parts of the set into the slate, while geophones and hydrophones record how the sound travels through rock, mud and water. The recorded response is then fed back into the live mix.