Uncovering the secret history of Wales' war bunkers; Lydia Morris unearths some startling stories about the north Wales bunkers that once protected people and national treasures from wartime attacks.
But while they may largely be forgotten by the public, they have all played a vital role in the nation's history.
Buried deep under north Wales' soil, far from the UK's major cities, they have protected the nation's treasures and its deadliest secrets.
From the hiding of the Crown Jewels and Leonardo da Vinci masterpieces to storing the bouncing bomb and aiding the development of nuclear weapons, they formed a protective shield from prying eyes and devastating bombs.
So we have taken a look inside these sites of huge historical interest to look back at some of the UK Government's best kept secrets.
| Manod Quarry, Blaenau Ffestiniog Beyond Manod Quarry's grey slabs of slate is a fascinating story of how millions of pounds worth of British historic masterpieces were kept safe deep underground at the height of World War II.
Across Europe treasured art was looted, bombed and burned during the war so efforts to protect the country's most artworks from the Nazi bombs were made by Churchill as soon as war was declared in 1939.
Among the items hidden deep in this Snowdonia mine were 19 Rembrandts, Van Dykes, Leonardo da Vincis and Gainsboroughs, as well as the Crown Jewels.
All the royal pictures from the palaces, the Tate and the National Gallery were also transported to the quarry - disguised in delivery vans for a chocolate company.
As soon as they arrived, purposedesigned squat brick "houses" were built inside the vast chambers to preserve the paintings in air-conditioned and heated safety.
Narrow gauge tracks were extended and specially designed wagons were built to carry the nation's treasures up the steep hill from Blaenau to the mine.
Two years before the war ended, a rock fall slightly damaged five paintings, resulting in the rapid evacuation of 700 others from that part of the quarry.
After that it was regularly inspected by engineers.
The whole operation was kept top secret until it was eventually revealed after the Government's lease on the quarry expired.
The masterpieces were returned to the walls in London as soon as peace was declared in 1945.
Manod proved to be so successful that, in the 1950s, it was the planned destination for Britain's art treasures in the event of a third world war.
| Rhydymwyn Valley Works, near Mold These former top secret tunnels at Rhydymwyn Valley Works housed thousands of mustard gas shells during the height of production during the war.
The Valley Works, which now sit in the heart of a nature reserve near Mold, were converted into a mustard gas factory by ICI on the orders of Winston Churchill.
Historians believe workers made up to 40,000 shells a week at the secret plant.
Partially due to its location near dense woodland, Rhydymwyn is the only site of its kind not discovered by the Nazi intelligence and therefore was not a target for German bombers.
But its role in Britain's secret history did not end there. Amateur historians from the Rhydymwyn Valley History Society unearthed proof that the miles of tunnels also served as home to the developers of the first atomic bomb.
The site, now part of a nature reserve, finally closed in 1994 and today, it is considered historically important.
Ten years ago next summer, some of the uninspiring brick buildings were given protected status by Welsh heritage body, Cadw.
Rydymwyn tunnel tours will open to the public in 2018 for five special tours in April, May, June, July and September.
Booking is required. Visit rhydymwynvalleyhistory.co.uk to book.
| Glyn Rhonwy Quarry, Llanberis As soon as World War II was declared, the disused Glyn Rhonwy slate quarry in the heart of Snowdonia became home to a secret munitions store.
The quarry pits, equivalent to the size of two football pitches, stored around 18,000 tonnes of weapons for the duration of the war.
When an RAF airbase needed ammunition for its planes, an order would be sent through to Glyn Rhonwy and be delivered by road or by rail. The site consisted of a number of deep open pits, linked together by tunnels.
Narrow gauge railway lines entered the lower level of the depot. It also had an underground depot and was adapted to produce a store with two floors throughout, with electric lifts transporting bombs to the upper floor.
In January 1942, two-thirds of the structure collapsed, burying 14,000 tonnes of bombs. The majority were recovered and although the remaining tunnels were eventually cleared of debris, no ammunition was ever stored underground at Llanberis again.
Some 30 years later in the 1970s, the site was used to dispose of old and surplus bombs, bullets and grenades.
It was confirmed that 70,000 German tabun nerve agent shells seized following World War Two were held at the Llanberis quarry for a short time before they were moved to another facility near Caernarfon, and eventually dumped at sea.
A PS100m hydro-electric power plant has recently been given the go head on the site, that has been disused for years. The scheme will generate electricity by releasing water from a reservoir on higher ground to a second, lower reservoir.
Building work could begin in 2018.
| Great Orme, Llandudno The Royal Artillery gunnery school was established on Llandudno's Great Orme the year after World War Two began.
It was relocated from Shoeburyness in southern England because of the potential threats of German invasion and Nazi bombings.
Designed by the Royal Engineers, the school trained officers and other ranks in coast artillery, radar technology, and assisted in the development of new weaponry and tactics.
Some of the ruins are still accessible via Llys Helig Drive near the West shore today, where gunners would practise firing huge guns out to toy-boat targets.
The bunkers stretch for a kilometre along the coast and were in full use until the end of the war.
The buildings, including the bunkers and a generator station, are what's left of the training base on the west shore today.
Seven years ago, the remains of the former Coastal Artillery School were protected by the historic buildings and ancient monuments body Cadw.
The scheduling is not the same as being granted listed status but will safeguard the site for posterity.
Cadw stated that the monument is considered to be of national importance as material evidence of the preparations for the defence of the UK in the war.
| Cold War Nuclear Bunker, Glyndwr University Few people are aware that under the floorboards of Wrexham's Glyndwr University lies a chilling relic of the Cold War.
At one of the most tense periods in British history soon after the Second World War came to an end, secret bunkers was built beneath what would have been the Denbighshire Technical College at the time to protect any survivors of the nuclear war so many feared in the '50s.
Had the threat of nuclear conflict become a reality during the Cold War, the bunkers would have been filled with the lucky few who may have escaped unscathed from the destroyed world above ground.
They could also have become a place to die for those who weren't so lucky and who had not responded to treatment in the university's art school - which would have been turned into a hospital under the emergency plan. And some sections could have been used as a temporary morgue to house the bodies of the fallen.
Thankfully, the horrors so many people lived in fear of for so many years never happened, but the bunkers remained one of the town's best-kept secrets for decades.
| Grange Cavern, Holywell During the height of the Second World War, the famous bouncing bombs used in the 1943 Dambusters raid on the Ruhr region of Germany, were secretly stored in a hidden underground cave near Holywell, Flintshire.
The purpose-built bomb was designed to bounce along the surface of water, like a skimming stone, to avoid obstacles placed in its way.
They were successfully used to destroy the mighty Mohne and Eder dams, wreaking havoc with the Ruhr's vital water supplies.
The operation was famously named the Dambusters raid.
The cavern also stored 11,000 tons of other World War Two bombs.
During the early 1980s, the old limestone cave in Holyway, near Holywell, was turned into the Grange Cavern Military Museum, where a whole host of military vehicles and equipment was on show 100ft below ground, before it closed in 1989.
<| Glyn Rhonwy Quarry, Llanberis, was used as a secret munitions store during World War II Arwyn Roberts
Inside the Cold War nuclear bunker underneath Glyndwr University)
<B Attendants carry out a routine inspection on a painting by Paolo Veronese at Manod Quarry in 1942. In the foreground is Cardinal Richelieu by Philippe de Champaigne Fred Ramage
<B In September 1942, art treasures from the National Gallery were moved to during World War II Manod Quarry slate caverns in Merionethshire for safekeeping Fred Ramage