A copper mine has struck gold by earning a place in the 50th anniversary edition of Guinness World Records.
Tourists can visit a section of the caves, but more of the mine is to be discovered.
The Great Orme Copper Mine has been named as the largest Bronze Age copper mine in the world.
Dating back up to 4,000 years, the mines have been excavated for the last 15 years.
"We've always been recognised by the academic world but are delighted to get public recognition in this way - and one which will go around the world,"
said director Ann Hammond.
Archaeologists are working on the site every day, which attracts students of the Bronze Age.
"Twenty years go, no-one thought copper mining took place in Britain during the Bronze Age. It's a place of continual discovery, and there are still tunnels to excavate," said Mrs Hammond.
Tourists can access 250 yards of the mining tunnels, as well as learning about the Bronze Age.
The mines were first uncovered in 1987 at Great Orme's Head near Llandudno.
OTHER GUINNESS WELSH RECORDS
Largest collection of Noddy items - 1,351 in Carmarthen
Most points in a rugby international career - Neil Jenkins, 1,052
Heaviest cabbage - Llanharry, 124 lb
Most Valentines sent to a guinea pig - Sooty, 206
At the end of 2002, archaeologists believed they found the largest prehistoric man-made cavern in the world, 130ft below ground.
Guinness World Records created a new category after verifying the mine's claim to be the largest with experts.
A spokeswoman said: "Quite a lot of our records are reactive - ones we are asked to check out - but this was something one of our scientific and research officers was interested in and went about investigating himself."
The record will be included in the new edition, which is published in September.