Grjotagja

Grjotagja is a fissure cave near Myvatn with clear blue water standing in the bottom, and it was a well used bathing place for local people through much of the twentieth century. That ended with the Krafla eruptions between 1975 and 1984, which pushed the water temperature well above anything bearable; it has cooled since but remains variable and unreliable, and the landowners prohibit bathing. Entry into the cave itself is by scrambling down through gaps in the rock. It appeared in Game of Thrones, which brought a large increase in visitors, and the pressure of that traffic is part of why the rules tightened.

What you actually see

• A fissure cave with clear water - blue in the light through the gaps.
• Bathing that ended in the 1970s - the Krafla eruptions overheated it.
• Private land with rules - swimming is not permitted.
• A filming location - the cause of the modern crowds.

When to go

May to September; the rocks are dangerous with ice in winter. Half an hour.

Honest expectations

You cannot swim here, whatever older guidebooks say, and the temperature is genuinely unsafe at times. The scramble in is on sharp rock in poor light. It is a ten minute stop that fills with coach groups. Facilities are a car park.

Nearby

Hverfjall and Dimmuborgir are minutes away; Myvatn itself is west.