Kerið is a 3,000-year-old volcanic crater lake on the Golden Circle route, famous for its neon-blue water, blood-red scoria walls, and vivid green moss. Unlike most Icelandic craters formed by explosive eruptions, Kerið was created when a cone volcano emptied its magma chamber and collapsed inward. The result is one of the most photogenic geological formations in Iceland — a near-perfect elliptical caldera measuring 270 metres across and 55 metres deep. It's the only Golden Circle site with an entrance fee (600 ISK), which funds path maintenance on the privately owned land. The acoustics inside the crater are so remarkable that Björk once performed a concert on a floating raft on the lake.
Story & Legend
Kerið sits within the Tjarnarhólar crater row, a chain of four volcanic craters along an 800-metre fissure in the Grímsnes area of south Iceland. Local folklore says the lake's water level rises and falls with the ocean tides, though geologists attribute the fluctuations to seasonal groundwater changes — the lake is fed from below, not by rainfall. In winter, the lake freezes solid and the crater becomes a snow-covered amphitheatre. The name Kerið roughly translates to "tub" or "vessel" in Old Icelandic, describing its perfect bowl shape. The surrounding land has been privately owned for generations and is now managed by Arctic Adventures, which purchased the site in 2023.
Geology & Science
Kerið is approximately 3,000 to 6,500 years old — young by Icelandic standards, which explains why its red volcanic rock hasn't yet oxidised to the typical black. The vivid red and orange slopes are caused by iron-rich scoria that hasn't been weathered by millennia of rain and wind like older formations. The caldera measures 270 metres (886 ft) long, 170 metres (558 ft) wide, and 55 metres (180 ft) deep. The lake at the bottom ranges from 7 to 14 metres deep depending on the season. Its striking aquamarine colour comes from dissolved minerals in the groundwater, not from algae — the water is surprisingly clear. Kerið is classified as a maar, meaning it formed through the collapse of a volcanic cone rather than an explosive eruption, which is why its walls are so steep and symmetrical.
Safety
The rim walk is short and easy on well-maintained gravel paths — allow 15 to 20 minutes to circle the top. The wooden staircase down to the lake is 139 steps with railing, but can be slippery when wet or icy. In winter, bring shoes with good grip or microspikes. Stay on marked paths — the volcanic rock on the crater walls is loose and brittle. Swimming in the lake is strictly prohibited for both safety and conservation reasons. There are no toilets or food facilities at Kerið itself, but the town of Selfoss is only 15 kilometres south with full services. Drone use is prohibited over the crater.
Photo Tip
Visit when the sun is high (midday in summer) for the most vivid lake colour — the aquamarine pops when directly lit. The contrast of red rock, green moss, and blue water is naturally oversaturated and photographs beautifully without filters. Walk the full rim for different angles: the eastern side gives the widest view, while the northern rim catches the best light in the afternoon. For the classic composition, descend to the lake level where you can frame the water against the towering red walls. Golden hour creates dramatic long shadows across the crater walls. In winter, a frozen lake with snow-dusted red slopes makes for an entirely different but equally striking shot.
Insider Tip
Arrive before 10am in summer to beat the tour buses — the Golden Circle coaches typically hit Kerið between 11am and 3pm. The entrance fee is 600 ISK per person (children under 12 free, groups of 10+ get 10% off). The crater is open during daylight hours only, which means limited access in winter. Combine Kerið with the Secret Lagoon in nearby Flúðir for a perfect half-day that most Golden Circle tours skip. In winter, check whether the lake has frozen — the sight of a completely white crater bowl is worth timing your visit for.
Best Time to Visit
Summer (June–August) for the most vivid colours and longest access hours. The aquamarine water is brightest under direct sunlight. Winter (November–February) for a completely different experience — frozen lake, snow-covered slopes, and far fewer visitors. Avoid midday in peak summer if you want the crater to yourself. The site is open year-round during daylight hours.
What to Bring
Casual clothing and comfortable walking shoes with good grip. The rim walk is easy but the descent stairs can be slippery. In winter, bring waterproof layers and shoes with traction or microspikes for icy steps. A windbreaker is useful year-round — the crater rim is exposed.
