Abandoned ‘sunken palace’ hidden and forgotten under popular UK seaside town

For well over a century people have walked across this famous patch of land in one of the UK’s most famous seaside resorts with no idea of what lies beneath their feet. But hidden underneath Llandudno’s Great Orme is a sunken reservoir. It’s no ordinary reservoir or underground lake; towering columns of brick rise from the water holding up arched roofs, all beneath the surface and so grand that it has been compared to “an underground cathedral”.

Fach reservoir was built in the 1800s and opened by the Prince of Wales on June 17, 1880. It was part of a programme of works to end water shortages that had long plagued the expanding seaside resort in north Wales. When in use, the reservoir was 12ft deep when full and it had a capacity of 936,000 gallons. To blend the facility into its landscaped surroundings, brick arches and a roof were added in 1914, creating a hidden, cavernous space, North Wales Live reports.

But after a while, “this vast hidden chamber” was no longer needed and was then drained and largely forgotten. Its grass roof later became a putting green but the reservoir below remained largely inaccessible for decades. Access was through a manhole, with ladders needed to climb down.

It has been compared to Istanbul’s great Basilica Cistern. Known as the Sunken Palace, it is the largest of several hundred ancient cisterns beneath the vast Turkish city. Like the Welsh version, there are also towering columns and brick-built arched roofs.

And now it is possible that Llandudno’s underground reservoir could become accessible to the public once more in the form of a new tourist attraction called Llandudno Vaults, a proposed year-round visitor attraction that will combine Victorian engineering, immersive storytelling and Welsh mythology. A new entrance would be created in an area now known as Happy Valley.

Although there have long been talks and rumours of the mostly-forgotten site becoming a tourist attraction, the plans have taken a significant step forward after the project secured a £20,000 grant, though significantly larger sums will be required to make the plans reality.

Andy White, managing director of Llandudno Vaults, said: “For more than a century, thousands of people have walked across Happy Valley without realising what’s beneath their feet. The reservoir is one of north Wales’ hidden engineering treasures, and our ambition is to reveal it in a way that respects its history while creating a completely new visitor experience.”

The team expects to submit a planning application later this year and has started engaging with local businesses, organisations and community stakeholders as the proposals continue to develop.

Conwy county councillor Sharon Doleman said: “The Llandudno Vaults project presents an exciting opportunity to unlock a hidden part of the town’s heritage and create a truly unique visitor experience.

“By combining Victorian history and engineering with Welsh culture, mythology and storytelling, it has the potential to become a distinctive year-round attraction that complements Llandudno’s existing tourism offer. The project could help attract more visitors, support the local economy, and showcase both the town’s rich heritage and the unique cultural stories that make North Wales so special.”

The Llandudno Vaults website says: “Beneath the Great Orme in Llandudno lies Y Fach, a long-forgotten Victorian reservoir built from red brick arches with vaulting so grand it feels like an underground cathedral. For decades this vast hidden chamber has been locked away, its potential unseen. The Llandudno Vaults project seeks to transform this unusual space into a landmark immersive arts venue, where Welsh myths and creatures are brought vividly to life through storytelling, music, and interactive technology.

“At its heart, the Vaults is about reimagining an extraordinary piece of local heritage as a stage for culture and imagination. Visitors will descend into an atmospheric world where water, echoing acoustics, and Victorian engineering merge with projection, sound, and performance. Here, audiences won’t simply be told stories — they will become part of them.”

The history of the underground reservoir goes back to St Tudno, the sixth century patron saint of of the seaside town, who lived as a hermit and survived on spring water. For centuries, spring waters from the reservoir were used by the area’s miners and farmers.

The town’s rapid expansion in the 19th century, driven by Victorian-era tourism, put a strain on resources, particularly water. In the second half of the 19th century, officials embarked on a grand scheme to deliver a “magnificent water supply” to Llandudno.

Analysing the water, Professor Frankland in 1880 said: “It is a most excellent water for dietetic and all domestic purposes. It is wholesome and palatable and contains only a very small amount of vegetable organic matter. It is exceedingly soft and therefore well adapted for washing.”

Surface reservoirs were built, including Y Fach, which was officially opened by the Prince of Wales on June 17, 1880. For more than three decades it remained an unremarkable facility but began to look out of place in an area developing all the time. In 1914, plans were drawn up for a roof supported by the brick arches and the reservoir was discreetly tucked away from view and slowly forgotten.

The Basilica Cistern is described as “one of the magnificent ancient buildings of İstanbul”. It was built by Roman Emperor Justinian I (527-565) and was nicknamed “Sunken Palace” due to its numerous marble columns rising from the water. It covers an area of approximately 10,000 square meters, is 140 metres long and of 70 metres wide. According to written sources, it was used to get water to the Great Palace where the emperors lived.