You’ve no doubt seen photos of Iceland’s Blue Lagoon, with people soaking in its warm, milky blue water. Heated geothermally deep within volcanic bedrock, the water is naturally enriched with minerals including silica, which gives it the distinctive colour. In 2012, National Geographic named the attraction one of the 25 wonders of the world.

But there’s another place to immerse yourself in water in Iceland that’s just as natural, maybe even more memorable and is on a different kind of “best of” list.

At a place called Silfra, you can snorkel or scuba dive through a natural crack or fissure between two of Earth’s tectonic plates. It’s said to be the only place on the planet where this is possible.

The water at Silfra is the opposite of the Blue Lagoon. It’s icy cold, colourless and crystal clear. Instead of coming from 2000m within the earth, it comes from the Langjokull Glacier, Iceland’s second-largest ice cap.

It takes decades for the water to seep into the ground from the glacier and travel 50km through volcanic rock before emerging at Silfra. That purifying journey means water so clear, it will take your breath away — if the cold doesn’t first.

That’s assuming you sign up for Arctic Adventure’s half-day snorkelling tour. It was the only tour I feared, yet also eagerly awaited, on my five days of back-to-back adventures in Iceland in early May.

Silfra is in Thingvellir National Park, less than an hour’s drive from Reykjavik, the capital. In early May, the air temperature is about 7C while the water at Silfra hovers between 2C and 4C year-round.

Despite the temperature, thousands of people come every year to snorkel or scuba dive in what is said to be the clearest water in the world. In 2021, PADI (Professional Association of Diving Instructors) named Silfra one of 20 best dive sites in the world. It’s still in its top 20 this year.

Wearing bulky drysuits, our group of five waddles to the metal staircase leading into what looks like a narrow inlet. Our guide, Will, jokes that our lips will soon resemble those of Angelina Jolie. Our hands might also get cold. Even though we’re wearing big mitts that look like crab claws, they’re not waterproof.

I brace myself mentally, but when my face touches the cold water, the shock feels electric. Then I notice what’s beneath me — jagged rock walls forming a canyon. It looks like someone took a giant cleaver and split the rock open. Bright green algae, which Icelanders call “troll hair”, covers some of the rock, every strand visible.

Floating along on a gentle current, we have 30 minutes or so to ponder the significance of what we’re seeing. It’s more than just a crack in some rock.

Iceland is one of half-a-dozen or so islands that are part of the Mid-Atlantic Ridge, a long mountain chain that’s mostly underwater. It separates the North American continental plate from the Eurasian continental plate, and at Thingvellir National Park you can see how those plates are drifting apart.

In 2004, UNESCO inscribed the park as a World Heritage Site, stating, “Its best-defined feature is a major rift, which has produced dramatic fissures and cliffs demonstrating inter-continental drifting in a spectacular and understandable way.”

At Silfra, I’m looking at one of those fissures through my mask.

It’s fascinating, but if snorkelling in cold water isn’t appealing — my fingers ached and I occasionally rolled onto my back to lift my hands out of the water — there’s another way to witness plate tectonics in this park. You can walk through the 8km-long Almannagja Gorge.

As I walk with Tanja Sol Valdimarsdottir, a specialist with Arctic Adventures, she tells me she comes here every Christmas with her family. “It’s a tradition.”

The cultural significance of Almannagja to Icelanders can’t be overstated. This is where the country’s Viking chieftains gathered for their annual assembly (Althing) to pass laws and settle disputes. Beginning around 930AD and lasting until 1798, leaders met here for two weeks every year, making this one of the world’s oldest national parliaments.

It’s easy to imagine those early Vikings here. The landscape feels powerful, even majestic. Cliffs frame a narrow canyon — the Almannagja Gorge — and Oxararfoss Waterfall plunges over one side. Fans of the TV show Game Of Thrones will recognise it from season four. The entire park is known as the spiritual centre of Iceland.

Whether you explore it on land, in the water, or both, it’s an unmissable part of this country.

Suzanne Morphet was a guest of Arctic Adventures.They have not influenced this story, or read it before publication.

Fact File

Arctic Adventures’ Silfra Snorkeling Tour in Thingvellir National Park is offered year-round from Reykjavik starting at $US137 ($1903) per person.

If you’d rather stay dry, Arctic Adventures’ Classic Golden Circle Full Day Tour includes Thingvellir National Park as well as Geysir Hot Springs, and Gullfoss Waterfall.

Available year-round from Reykjavik starting at US$121 ($171) per person.