25 years since the Queen opened the Conwy road tunnels
They are basically two underwater boxes. And while the Conwy Tunnels may be no frills aesthetically, they are an engineering marvel and a community "lifeline".
The Queen officially opened the pioneering £190m passage around the north Wales bottleneck town of Conwy 25 years ago.
The tunnels skirt around the World Heritage-listed castle and are sunk on to the bed of a river which is home to Conwy mussels.
"God bless the Conwy Tunnels, they are up there with the greatest things to have happened to north Wales," insisted North Wales Business Club chairman David Williams.
"Their impact on north Wales has been transformational, they are a total lifeline. The economic and community enhancement benefits are priceless.
"Without them, we'd be out on a limb and up the estuary without a paddle."
It was a project of firsts: at the time they opened, the tunnels had been the subject of the longest public inquiry into a road scheme, they were the UK's most expensive road project and the UK's first prefabricated, immersed tube road tunnels.
"The Conwy Tunnels were one of the biggest civil engineering challenges in the country due to the environment," recalled Brian Hawker, the Welsh Office's former head of roads.
"I remember the Queen was very impressed and her opening the tunnels emphasised how important this project was to, not just Wales, but the country as a whole."
The publicly-funded £700m A55 North Wales Expressway which runs through the three-quarter-of-a-mile Conwy Tunnels has quickly become the main artery for north Wales to the English motorway network.
Conwy was once more renowned for its traffic congestion than its 13th Century castle. Traffic jams choked the streets as cars struggled to squeeze, one at a time, through Conwy's historic town walls.
The River Conwy already had three crossings, including Thomas Telford's historical 18th Century suspension bridge, but the newly-formed Welsh Office made a commitment to a new route because it was so crucial to making the A55 dual carriageway a near-motorway standard highway.
"We only had a small opening to build the crossing due to hills on the south of Conwy and the sea to the north," Mr Hawker said.
"The public inquiry found building another bridge would detrimentally affect the view of a World Heritage Site so that plan was rejected.
"But building a tunnel would harm the estuary ecology where mussels and salmon are farmed. The River Conwy also has a huge tidal range.
"The compromise was to build the first immersed tube tunnel in Britain and only the second in Europe."
The late Lord Roberts of Conwy, then Minister of State for Wales Wyn Roberts, signed the £102m main Conwy Tunnel contract - then Britain's biggest road deal - at the Castle Hotel in Conwy before the five-year construction project started in 1986.
"The dry dock in which the six prefabricated sections were made was bigger than Conwy itself," added Mr Hawker.
"We had to move live ammunition, shells and grenades as the basin was a First World War army camp. Part of the Mulberry Harbour, used for the D-Day landings in Normandy, was also prepared there.
"The six prefabricated concrete sections, which each weigh 30,000 tonnes, are each half the size of the Millennium Stadium.
"Once built, the dry dock, which is now Conwy Marina, was flooded and each section towed into position with precision.
"They were then sunk to the bottom of the river with the help of divers working in almost zero visibility. The bolts joining them were the biggest in the world at the time."
End of the 'safari'
The Conwy Tunnels are the centrepiece of an A55 expressway described as "probably best example of a major civil engineering challenge that you can find anywhere in the UK due to the dramatic environment".
"It changed north Wales overnight," insisted David Williams, who is also a member of the Welsh Industrial Developmental advisory board.
"Getting in and out of the north west was previously a safari which took the best part of a day. It opened us up to the world as possible four-hour journeys can now be done in under an hour."
"The cost was enormous because the challenge was so huge," said Mr Hawker.
"Every authority in north Wales cooperated to build the A55 because the inward investment benefits for industry, tourism and commuting were so enormous."
The A55 project has won many prestigious engineering awards including the global Construction Achievement awards twice
"The Conwy tunnel's only problem is its success," concluded Mr Williams.
"The A55 is reaching its capacity, especially with the number of huge lorries trundling to and from Holyhead harbour.
"While the traffic headaches of Conwy have gone, the queues are overflowing elsewhere and the A55 is in danger of being unfit for purpose within 10 years.
"North Wales' authorities are part of the North Wales Ambition Board and are trying to access Westminster funds to ensure our transport infrastructure is suitable for the 21st Century and that we can capitalise on the government's Northern Powerhouse plan."