Blue ice cave Iceland, from Jökulsárlón

This tour visits Breiðamerkurjökull, an outlet glacier of Vatnajökull on the south-east coast. You meet the guide next to the cafeteria at the Jökulsárlón Glacier Lagoon ticket office, ride 45 minutes by super jeep to the glacier, spend about 100 minutes there on a guided walk to the cave, and ride 45 minutes back. Helmets and crampons or micro-spikes are handed out after a safety briefing.

Ice Explorers runs this cave tour from October to April. The cave may lie at the very edge of the glacier or need a short walk of 500-1000m on the ice, and walking on the tour adds up to 1-4 km in total. Which cave you enter is decided by the guides on the day, from the caves that winter has made safe to visit.

Breiðamerkurjökull flows from it straight toward the sea. At its farthest, after advancing until the 18th and 19th centuries, only about 250 meters separated the glacier from the ocean. Today it calves into Jökulsárlón, which the park calls the largest and most active glacial lake in Iceland, at the mouth of a trough 200-300 m deep and 25 km long.

The whole landscape is protected. Breiðamerkursandur joined Vatnajökull National Park in 2017, and the park was inscribed on UNESCO's World Heritage List on 5 July 2019 under natural criterion (viii). Park rangers supervise Jökulsárlón every day of the year and are responsible for the ice caves in Breiðamerkurjökull. Every Vatnajökull ice cave you can visit from the lagoon lies inside this World Heritage site.

The second theme is variety. More than a few reviewers write that they visited several caves on the same tour, each with a different shape, and describe the colors as stunning and blue. The super jeep itself gets praise as well: for some, the ride in a huge truck across to the glacier was a highlight before the ice even began.

Not every review is glowing. A traveler who wrote a 4-star review found the time inside short and the glacier busy, with other groups waiting for the same entrance. That matches what the listing itself says: the glacier changes constantly, so the caves may not look like pictures taken months or years before.

Inside the season, the caves keep changing. Ice Explorers says that from season to season, and even within a season, the caves change: old ones disappear and new ones form. A cave that fills social media in January may be gone by March, replaced by another the guides find safer or more beautiful.

Winter also means short days. Around the lagoon the sun stays up for only about 4.3 hours at mid-December and 5.4 hours at mid-January. Ice Explorers runs two departures a day, one in the morning and one right after noon.

The people who guide you are trained for this. Ice Explorers says all of its glacier guides are professionally certified by the Association of Icelandic Mountain Guides. Visit Iceland's advice is the same as the guides' own: visit an ice cave only with professional glacier guides and the right equipment.

Weather in the park can turn quickly. Vatnajökull National Park warns that conditions can change suddenly and that roads can deteriorate from flooding, sandstorms and even snow at any time of year. Plan the cave early in your stay near the lagoon, and hold a spare day in reserve when the ice is the main event of your holiday.

The group is capped. The listing is limited to 14 participants with a live guide speaking English. On its own site Ice Explorers gives 12 people per guide for this tour.

One term deserves attention before you go. Rain trousers, rain jackets and hiking boots can be hired where the tour meets, and a guest who is not dressed for the glacier may have to rent gear or, in extreme cases, be refused for safety, with the cancellation policy applying. Read the clothing section below and arrive ready.

Expect a mix of colors rather than pure blue. Ice Explorers describes formations on its tours that range through bright blue and emerald green to black ice. NSIDC's caption of a Breiðamerkurjökull cave names the blue of pure ice, the white of fresh snow and the black of volcanic ash trapped by the glacier.

Inside, light is low and hands get cold. Turn off the flash to keep the natural color, brace your phone against your body or the ice for sharper shots, and keep a spare battery in an inside pocket. Your guide knows the angles, and one reviewer says the guide took the photos for the group.

Dress for a walk in wind and wet. The listing recommends warm, preferably waterproof clothing and sturdy walking or hiking boots, and asks you to bring warm clothing, hiking shoes, weather-appropriate clothing, a camera and travel insurance. Safetravel's rule fits well: wool and synthetics, no cotton.

The technical gear is provided: transportation in a 4WD, a guide, helmets, crampons or micro-spikes and a safety harness if needed. Clothing and shoes are not included, but rain gear and boots can be rented at the meeting point before departure.

Route 1 runs straight through Breiðamerkursandur, and the park says the region is accessible year-round. Winter driving still needs care: Safetravel notes that a 4x4 can help in some conditions but does not remove the risk of skidding on ice, and the park recommends winter, all-year or studded tires.

Pickup from your accommodation is not included, so you arrive at the meeting point on your own. Sleep nearby the night before, in Höfn or around Skaftafell, and the cave becomes a relaxed half day instead of the end of a long drive.

Some of those icebergs are very old ice. NASA notes that a few are thought to be more than 1,000 years old, and that while many are white, some are electric blue with black streaks of ash from past eruptions. Watching them is the perfect way to fill the time before a tour.

A quieter lagoon lies nearby. Fjallsárlón, in front of Fjallsjökull on the same Breiðamerkursandur plain, is 10 kilometers from Jökulsárlón. With winter days as short as they are, choose one lagoon in daylight and leave the other for your drive onward.

It is not for everyone. The listing says it is not suitable for children under 7 or anyone under 135 cm, pregnant women, people with mobility impairments or heart problems, or wheelchair users. Ice Explorers' longer exploration tour sets a higher minimum age of 13 and walks 4-6 km.

Keep expectations honest. Nobody can promise a particular cave or shade of blue, and one reviewer found the glacier busy and the time in the cave short. If you come for the experience of standing inside a living glacier with a good guide, the reviews suggest you will leave happy.