Wales& #39; capital city has a closely-guarded, 10,000 year-old secret.

Partly because it& #39;s extremely dangerous, but also because to discuss it openly would be to acknowledge a surprising, yet disconcerting legacy:

Cardiff& #39;s hollow mountain.

THREAD https://abs.twimg.com/emoji/v2/... draggable="false" alt="👇" title="Rückhand Zeigefinger nach unten" aria-label="Emoji: Rückhand Zeigefinger nach unten">

Humanity has quarried this Morganstown mountainside since the Stone Age.

Standing at 210m (690ft), the Lesser Garth is a geological marvel.
A limestone ridge, its dolomite formations have left a vast labyrinth of uncharted tunnels, hidden chasms and subterranean lakes.

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> Dolomite explainer https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke">
• A sedimentary rock composed of the mineral of the same name
• Also known as "dolostone"
• Formed when limestone undergoes a series of chemical changes
• Serves as host rock for iron, lead, zinc, copper deposits
• A prized mining asset

Millennia of quarrying through primeval caving complexes has resulted in spectacular voids.

A jaw-dropping, multi-level warren of cathedral-like spaces and panic-inducing cavities yawn through the ridge of hills marking the southern perimeter of south Wales& #39; historic coalfields.

Decades of recent industrial activity has decimated much of Lesser Garth& #39;s original cave system.

But nothing compares with the aerial view.

The verdant wooded slopes seen from the A470, Wales& #39; major north-south carriageway, are merely cosmetic…

Because there is little beyond.

Lesser Garth cave, also known as Ogof Tynant, is a dangerous subterranean system located on private land.

More https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts">

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/20/cardiffs-hollow-mountain/
https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" https://abs.twimg.com/emoji/v2/... draggable="false" alt="🚛" title="Sattelschlepper" aria-label="Emoji: Sattelschlepper"> https://dicmortimer.com/2014/01/13/cardiffs-quarries/
https://dicmortimer.com/2014/01/1... class="Emoji" style="height:16px;" src=" https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛰" title="Berg" aria-label="Emoji: Berg"> http://www.ogof.org.uk/lesser-garth-cave.html
https://www.ogof.org.uk/lesser-ga... class="Emoji" style="height:16px;" src=" https://abs.twimg.com/emoji/v2/... draggable="false" alt="👷" title="Bauarbeiter" aria-label="Emoji: Bauarbeiter"> https://www.dailymail.co.uk/news/article-2825771/Chambers-secrets-Amazing-images-weird-wonderful-caves-run-40-miles-underneath-south-Wales.html">https://www.dailymail.co.uk/news/arti...

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" " title="Lesser Garth cave, also known as Ogof Tynant, is a dangerous subterranean system located on private land.More https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts">https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" ">

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" " title="Lesser Garth cave, also known as Ogof Tynant, is a dangerous subterranean system located on private land.More https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts">https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" ">

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" " title="Lesser Garth cave, also known as Ogof Tynant, is a dangerous subterranean system located on private land.More https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts">https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" ">

https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" " title="Lesser Garth cave, also known as Ogof Tynant, is a dangerous subterranean system located on private land.More https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts">https://abs.twimg.com/emoji/v2/... draggable="false" alt="⛏" title="Spitzhacke" aria-label="Emoji: Spitzhacke"> https://thediff.blog/2018/11/2... class="Emoji" style="height:16px;" src=" ">

This thread is part of a wide-ranging new series entitled “Secrets of Wales.”

The full collection, spanning 220 million years, is here (please share what you love!) https://abs.twimg.com/emoji/v2/... draggable="false" alt="👉" title="Rückhand Zeigefinger nach rechts" aria-label="Emoji: Rückhand Zeigefinger nach rechts"> http://bit.ly/SecretsOfWales ">https://bit.ly/SecretsOf...