We are all familiar with the bewildering beauty of North Wales.
But that beauty is not just skin deep so to speak.
Beneath our feet is a secret world of subterranean adventure.
Whether it's a world-first underground trampoline park, prehistoric caves and the world's longest underground adventure - there's plenty to do below the ground as well as above it.
And in his newest travel guide, explorer and writer Peter Naldrett discovers the most exciting subterranean gems as he explored the hidden depths of the UK.
His definitive guide to the best days out underground are not just for intrepid potholders, but offers something for everyone.
So, here are six of Naldrett's top suggestions to explore in North Wales...
Bounce Below
The only subterranean playground of its kind in the world - Bounce Below deep inside the former Llechwedd Slate Caverns in Blaenau Ffestiniog, is an adventure only experienced in North Wales.
Twice the size of St Paul's Cathedral, the vast cavern has a number of large bouncing zones - each connected by a series of stairways and slides - that are suspended high up in the slate cavern, illuminated by LED lighting.
And for thrill seekers looking for an ever bigger challenge, below the bouncing nets is a high ropes experience. Despite being below the Earth's surface, the drop is still very significant to the bottom of the mine.
The "atmospheric lighting" is described by Peter Naldrett as giving the cavern an "otherworldly dimension", while he says the obstacles are "stunning, often with terrifyingly steep drops beneath".
The caverns were used for slate quarrying over many decades but had been dormant since the 1960s.
They had only been seen by visitors on a previous deep mine tour as they passed by on the underground train before Bounce Below opened in 2014.
Earlier this year, Bounce Below was used as the set for the first game show if its kind to be filmed.
Visitors must book in advance. Prices start from £20 per person and is only suitable for children over the age of 10.
Llechwedd Slate Caverns Deep Mine Tour
Deep inside the former Llechwedd slate caverns, thrill seekers can experience a tour into the vast mine - the steepest cable railway in Britain, taking you hundreds of feet underground.
Experienced from the point of view of the mine workers, the tour uses cutting-edge enhanced reality technology to tell the story of their blood and guts, their determination and resilience, their risk and endeavour.
The tour takes around one hour and finishes with a visit to the Mill.
And for those feeling brave enough, there is the option to take a ride in a military 4x4 truck to explore the formidable slate mountains above the surface.
The Quarry Explorer is an off-road adventure that goes right into the heart of the man-made mountains.
Mining began here in 1846 and in the Victorian times when slate production was at its height, around 17,000 workers were employed at the mine.
It produced material that were used on buildings all around the world, until the lack of demand hit it hard in the aftermath of the First World War.
Peter Naldrett, says: "The Llechwedd slate mines are a hive of activity. As well as learning about the historic slate mine, people come here to take part in extreme adventures."
Go Below
Test your nerve by venturing below ground on the longest underground adventure in the world.
With a number of subterranean challenges - the five kilometres long the course in Betws y Coed includes the planet’s deepest zip wire, a seated zip ride, a 70ft freefall, and the deepest accessible point in Britain, 1,300ft underground.
One of the most terrifying sections is the underground freefall, a 70ft sheer cliff.
The choice is to abseil down or for the brave there is the option to freefall where visitors will plummet before the freefall machine applies the brakes close to the bottom.
But the most popular adventure is the Go Below Challenge - a journey which takes you 1,300ft below the surface of Tanygrisiau up to the summit of Snowdon over 14 emotionally-charged, exhausting hours.
Peter Naldrett simply says: "It is not for the faint-hearted".
Opening times for the Conwy Falls Forest Park adventure does vary, depending on the tour. Prices start from £49 - depending on the challenge.
Corris Mines Explorers
During its heyday in the late 1800's, Braich Goch slate mine in Corris - a village in the south of Snowdonia in Gwynedd - employed 250 miners.
The early years were difficult and four different companies failed before the opening of the Corris Railway in 1859, and the establishment of the Braich Goch Slate Quarry Co. in 1864.
In one of its best year, the mine produced 7,000 tons of slab and roofing slate, which was dispatched around the world.
But rising costs and falling demand saw the company collapse in 1906. Another six companies worked the mine intermittently until it was finally abandoned in 1970.
Now, almost 50 years after it closed, adventurers can go deep into the mines to explore levels four, five and six.
Describing the attraction as an adventure with a "real sense of pace" in the book, Peter Naldrett, writes: "Evidence of the miners can be seen everywhere, from candles placed on the walls to discarded cigarette packets and drinking vessels.
He added: "Huge spaces were cut away by miners over many decades, revealing extraordinary areas that today are a remarkably beautiful highlight of the tour. In one of them, you can gaze up and actually see daylight through an opening high above.
"A tree grows on the edge of the gap, providing one of the most surreal sights you will see in this country from beneath the ground."
Corris Mines Explorers is open all year round, although tour times do vary. Prices start from £8.50 and is not suitable for children under the age of eight.
Great Orme Mines
The prehistoric caves date back almost 4,000 years are one of the most significant archaeological discoveries of modern times.
The Bronze Age site in Llandudno was hidden underground until excavations took place in the late 1980s. It is believed to be the world’s largest prehistoric mining site.
Archaeologists say they changed views about the ancient people of Britain and their civilised and structured society 2,000 years before the Roman invasion.
Over the past 22 years mining engineers, cavers and archaeologists have been slowly uncovering more tunnels and large areas of the surface landscape.
There are around nine levels of Bronze Age mines at the site, but only the top two are visited on the tour toady, where visitors can wonder along the prehistoric tunnels that were hand-dug to follow the copper deposits.
Peter Naldrett, says: "They key thing to remember is the tunnels themselves would once have been solid veins of copper ore. The early miners arriving here 4,000 years ago, would have followed the veins into the hillside and not wasted their time extracting material that wasn't useful."
King Arthur's Labyrinth
Voted the best visitor attraction in mid Wales in the National Tourism Awards for Wales last year, King Arthur's Labyrinth takes you on a boat through an underground waterfall, deep into a "mythical world".
Based on the sixth level of Braich Goch slate mine in Corris, visitors are guided by a boatman through the dramatic underground setting of huge caverns and torch-lit tunnels where tales of King Arthur and other ancient Welsh legends unfold.
Peter Naldrett describes the adventure as an "old fashioned storytelling experience", "wrapped around ancient myths and entangled in legends surrounding Kind Arthur".
He says there is a "startling amount of equipment left in situ by workers who hoped to return to a job" beneath the Welsh mountains one day.
"The key moment of the boat ride is the passage beneath the waterfall, a visual metaphor which transports you from the modern era into days or yore," he adds.
The mine that stays at a constant 10C lies beneath southern Snowdonia in Corris, Gwynedd.
Booking in advance is required and opening hours are from late March until early November from 10am until 4.45pm.
Prices per person are between £8.55 and £13.20.
