Arguably the most iconic caldera lake in the United States, this natural wonder is the main attraction in the appropriately titled Crater Lake National Park. The 2,148-foot-deep lake was formed around 5,667 B.C. after the eruption and collapse of Mount Mazama.
Before its destruction, the stratovolcano was regarded by the local Klamath Native American tribe to be the god of the underworld, known as Llao. The collapse of the mountain was witnessed by the Klamaths, who recorded it as a great battle between Llao and their sky god, Skell.
Blue Fire Crater, Kawah Ijen Volcano, Indonesia
Don't let the beautiful mint green hue of this crater lake deceive you. The picturesque Kawah Ijen is actually filled with sulphuric acid, and it lays claims to being the largest highly acidic lake on Earth, according to the Smithsonian's Global Volcanism Program. With all that sulphur washing up on the shore, it also the home of an active sulphur mine. It's common to see miners hand-carrying large baskets full of bright yellow chunks of solid sulphur uphill from the lake's shore.
The crater has become a popular tourist destination in recent years, thanks in part to global publicity generated around its famous blue fire, which is the result of sulphuric gas igniting as it escapes cracks in the ground.
Mount Katmai, Alaska
This remote crater lake situated in the caldera of a 6,716-foot-high stratovolcano is found in southern Alaska's Katmai National Park and Preserve. Measuring about 6.3 miles in diameter, the Mount Katmai caldera was formed in 1912 after the first-time eruption of the nearby Novarupta volcano.
Okama Lake, Mount Zao, Honshū, Japan
The bright turquoise hue seen in the photo above is just one of many colors the water takes on at Okama Lake, which is also known as the "Five Color Pond." Formed by a complex volcanic eruption in the 18th century, this natural treasure of Japan measures about 1,200 feet in diameter and 200 feet in depth.
Lake Tritriva, Vàkinankàratra, Madagascar
Located 30 minutes outside of the city of Antsirabe, this small yet breathtaking volcanic lake is surrounded by steep cliff walls of gneiss rock. While it's possible to swim in the lake, the water is cold and very, very deep — over 160 meters deep, to be exact. To understand the scale of that measurement, check out this video of a man bungee jumping off a 160-meter-high bridge.
Kerid, Grímsnes, Iceland
Iceland is full of surreal, otherworldly sites, and this beautiful crater in the country's Western Volcanic Zone is definitely one you shouldn't miss. Known as "Kerið" in Icelandic, this shallow, mineral-rich lake is surrounded by steep red volcanic rock walls sparsely covered in moss and other vegetation. While the caldera itself is about 55 meters deep, the actual water depth fluctuates between 7-14 meters depending on rainfall amounts.
The best way to see Kerid is to travel along a popular tourist route called the Golden Circle, a 300-kilometer loop that covers the most amazing natural sites in southern Iceland.
Kelimutu, Flores, Indonesia
There are three volcanic lakes found on Kelimutu — the image above shows Tiwu Ko'o Fai Nuwa Muri (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched Lake), which are separated by a single crater wall. The other is called Tiwu Ata Bupu (Lake of Old People)
What's extra interesting about this lake trio is that they are different colors despite being on the crest of the same volcano. The color changes are attributed to chemical reactions between lake minerals and changing volcanic gases.
Quilotoa, Andes mountains, Ecuador
Formed after a catastrophic volcanic eruption about 800 years ago, this watery caldera is well on its way to becoming a prime tourist destination. The turquoise lake at the center of the crater is well worth the drive and hike, though due to the acidity of the lake, a celebratory swim would be out of the question. Regardless, the view from along the rim is truly a sight to behold!
Formerly known as the Chubb Crater, Pingualuit is a relatively young impact crater, geologically speaking. The meteor impact that formed it is estimated to have occurred about 1.4 million years ago (give or take 100,000 years), which puts it firmly in the Pleistocene epoch.
Surrounded by a desolate, tundra landscape, the lake is one of the deepest lakes in North America, as well as one of the purest and clearest freshwater lakes in the world. A secchi disc, an object used to measure water transparency, can be seen as far down as 35 meters below the surface.