Quick answer: Sleipnir's natural Neptune Ice Cave on Langjökull is open for 166 days a year: 1 November to 15 April. Winter is when the ice is stable enough to enter safely, so that's what sets the dates. Plan around this window if you want the real cave.

Why does the natural ice cave only open for part of the year?

The natural ice cave on Langjökull glacier is formed by meltwater flowing through the glacier during the warmer months. In winter, temperatures drop and meltwater production decreases, allowing the cave to become accessible. The cave is naturally formed, so its size, shape and conditions can change from one season to the next. The season, 1 November to 15 April, is the window when that's consistently true.

What happens to the cave between April and November?

Between April and November, increased glacier meltwater changes the natural ice cave on Langjökull. Meltwater flows through and around the cave, causing the ice to melt and reshape the passages. Because the cave is naturally formed, it may shrink, collapse or disappear completely during the summer. A new natural ice cave may form in a different location or even in the same location before the following winter. For this reason, the natural ice cave is not accessible during the summer months and is explored only during the winter season. Outside ice cave season, Sleipnir still runs glacier truck tours on Langjökull, just without the cave itself.

How is this different from an ice cave that's open all year?

If a cave is open every day of the year, it was not made by the glacier. People dug it out and keep it in shape  People dug it and took care of it. But the ice in the walls is real glacier ice, formed naturally over hundreds of years. That can still be a great tour, but it is a different thing from a natural cave.

When should you book if you want the natural ice cave?

We recommend booking the natural ice cave tour as early as possible to secure your preferred date. The season is short, December through February carries the heaviest demand of the winter, and a four-hour round trip from the Gullfoss upper car park needs to be built into your itinerary ahead of time. Free cancellation up to 24 hours before departure means booking early doesn't lock you in if your plans shift.

Does the cave look the same every winter?

No. Because it's shaped by meltwater and glacial movement rather than built to a fixed design, the cave can look different from one season to the next, and sometimes even within the same winter. Your guide explains why the cave looks different from the previous season and how it has changed over time. 

Frequently asked questions

When does the next season start and end? The natural ice cave is open from 1 November to 15 April. 

Can I do a glacier tour with Sleipnir if the ice cave is closed? Yes. From 16 April to 31 October, Sleipnir runs truck tours onto Langjökull without the cave, using the Red Glacier Monster Truck along with fun activities such as sledding and glacier golf .

Does booking early guarantee a spot during the busiest winter weeks? It improves your odds considerably. The departure point and group sizes are fixed well ahead of each date, so popular weeks, especially around the winter holidays, can fill up quickly. fill before the season even opens.

Why can't an operator just build a natural ice cave that stays open year-round? 

A natural ice cave is created by the glacier itself and changes with the seasons. Summer meltwater can reshape or melt the cave, so it cannot remain open year-round without human construction and maintenance. An ice cave that is regularly built or maintained by hand is a different product from a naturally formed glacier cave.

The Neptune Ice Cave on Langjökull is a genuine natural ice cave, open from 1 November to 15 April. The tour with Sleipnir Monster Truck starts at Gullfoss and requires no hiking or snowmobiling.

See you on board the Sleipnir Glacier truck!