ST. JOHN'S, N.L. -- Visitors from across Canada and around the world were awestruck as their tour boat steamed within view of a mammoth iceberg off Cape Spear, N.L.

They had lined up at a pier in St. John's for their chance to view the best season for big ice off the province in at least a decade.

The sight of a giant glacial sculpture moored in 50 metres of water, a perfect archway carved right through it by surf and waves, did not disappoint.

"Absolutely beautiful -- never seen anything like it before," said Pete Kottenstette, who relocated to Mount Pearl, N.L., from Dallas as part of his work in the oil and gas sector.

Jean-Pierre Renaud of Laval, Que., was equally impressed.

"It's incredible. It's just beautiful, seeing the size of it, the colours coming out of it when the sun is on it, it's just amazing. It's breathtaking."

Prehistoric towers and slabs of ice moulded by the sea into shapes of all description have arrived to the delight of tourists as mariners take warning.

"It's phenomenal, really," said Capt. Barry Rogers, president of Iceberg Quest Ocean Tours, as he paused from a hectic schedule in the wheelhouse of his popular vessel.

"We've had some great ice years, but I think this one is going to be the biggest year of all. We've just had a huge flow of icebergs coming from Greenland."

The rare display of frozen natural beauty is attracting people from across the globe, Rogers said.

"Folks are coming from all over the world. They're just totally intrigued with icebergs.

"I guess it's one thing to hear about them and yet it's a totally different thing to be up within several hundred feet of them."

But Rogers is careful to keep a safe distance.

"That iceberg is quite large underneath and quite dangerous as well," he told his guests over a microphone as he approached the site where it ran aground near Cape Spear. It's gorgeous to look at but can break apart or roll over with little warning, he explained.

Rogers also cautioned passengers in the rise and fall of North Atlantic swells to hang on at all times. One hand on the camera, one hand on a safety rail, he urged them.

As people crowded the pulpit bow taking photos, Rogers pointed out the berg's striking shades of brilliant aqua and deep blue, the grooves cut by waves and small waterfalls running from melting sections.

He said it likely took around 18 months to three years for that iceberg to arrive.

Creeping glaciers that cover much of Greenland crawl towards ocean cliffs before snapping off in giant slabs that then float south toward the coasts of Labrador and Newfoundland. When spring sea ice is especially thick it keeps the icebergs, believed to be at least 12,000-year-old specimens of pristinely pure water, more intact as they travel.

They float because the density of the frozen berg is less than that of sea water.

Smaller "bergy bits" are especially hazardous as they can be harder to see in waves but can easily cut through a steel hull.

Rogers steered toward a soaring rocky cliff to give passengers a closer look at a sparkling piece of sunlit ice less than five metres long. Such remnants are known as "growlers" for how they hiss as they melt, releasing air.

Trudy Wohlleben, a senior ice forecaster for the Canadian Ice Service, said a long trail of bergs extending down the Labrador coast is now concentrated off northeastern and eastern Newfoundland.

She said it's the most sea ice and resulting bergs since 2003, though it's not clear why.

"Climate has many aspects to it," Wohlleben said from Ottawa. "Whether it's natural variability or it's part of a longer term trend, it's a little difficult to say."

It's expected that icebergs will be visible off Newfoundland for at least the next several weeks.

If you go:

Check out the Iceberg Finder map at the website icebergfinder.com for updates.

A warm coat, hat and gloves are recommended for offshore viewing.