Silfra Fissure

Silfra is a crack in the floor of Thingvallavatn opened by the two plates pulling apart, and what makes it famous is the water. Meltwater from the Langjokull glacier travels underground through porous lava for decades before surfacing here, which filters it so thoroughly that visibility routinely exceeds a hundred metres - snorkellers and divers report being able to see further than the fissure is long. It holds around two degrees year round, so dry suits are compulsory and the season is irrelevant. The much-repeated line about touching two continents at once is a simplification: the plate boundary is a zone tens of kilometres wide, not a single crack, though the fissure is genuinely part of that rifting.

What you actually see

• Visibility beyond a hundred metres - meltwater filtered for decades through lava.
• A rift opened by plate spreading - part of the boundary zone, not a single seam.
• Two degrees all year - dry suits compulsory in every season.
• Thingvellir around it - the World Heritage assembly site above.

When to go

All year. Half a day.

Honest expectations

Snorkelling and diving are guided only and must be booked; dry-suit certification is required for diving. It is genuinely cold - hands and face take the worst. The two-continents line is marketing shorthand. Numbers are capped and slots fill.

Nearby

Thingvellir's assembly site is alongside; the Golden Circle continues east.