The world is full of mountains: big, small, steep, covered with ice or jagged cliffs. All things to consider when you’re thinking about ascending one.

Here are the world’s most impossible mountain faces to climb.

K2

Not to be confused with Kilimanjaro, which is Africa’s highest mountain, K2 is part of the Himalayas in northern Pakistan. K2 is the world’s second-highest mountain behind fellow Himalayas peak Mt. Everest, but K2 is even more difficult thanks to the technical difficulty of circumventing its glaciers, seracs — which are huge ice pillars — and generally frozen surface. Because of the ice and complex geology of the mountain, parts of it are prone to collapse and movement at all times, meaning that climbers need to be especially poised and alert to ensure they don’t end up getting caught in the movement. To make matters worse, weather at K2 tends to be unpredictable and violent — as if there needed to be another obstacle.

Nanga Parbat

Nanga Parbat, one of the so-called “eight thousanders,” because of it’s 8,000-meter-plus summit, also has a couple of telling nicknames: “the Killer Mountain” and “the Man Eater.” Nanga Parbat is an incredibly steep and treacherous mountain, craggy with ice and rocks, and one of its three faces, known as the Rupal Face, is colloquially thought to be the highest mountain face in the world. Watching the video, you can see the dangers of climbing even the most seemingly harmless parts of the mountain; if you slip or lose your footing, or the ground underneath you moves, it can send you sliding toward either against unwelcoming surfaces of the mountain or down one of the massive rock faces. Thanks to the incredibly steep dropoffs, any fall would most likely be fatal. No one has ever climbed Nanga Parbat in winter.

The Eiger

The north face of the Eiger, in the Bernese Alps in Switzerland, has entered mountain-climbing lore as one of the most difficult climbs in the world. And unlike Nanga Parbat and K2, you don’t need to fly all the way to Pakistan to get there. The north face is correctly referred to as Nordwand, or North Wall, but because of its treachery it has been rechristened Mordwand — Murder, or Murderous, Wall. Climbing the face requires enormous amounts of strength and technical skill, since its incredible steepness means that any climber who is swept off the wall — whether by wind or the frequent avalanches and other phenomena that affect the mountain — will almost certainly perish. Even though the Eiger doesn’t quite match up to the most difficult peaks of the Himalayas, the unpredictability of the Mordwand maintains its reputation of extreme treachery.

Mt. Vinson

In case a mountain peak on one of the world’s more accessible six continents doesn’t interest you, there’s Mt. Vinson, the highest summit in Antarctica. Unlike the other mountains on this list, Vinson isn’t a particularly challenging climb in and of itself: the extreme difficulty here comes from the fact that it’s located in the Antarctica, and comes with the extreme cold and aggressive weather that you might expect from the frozen continent. The whole mountain is covered in ice and snow, and temperatures tend to remain around -20 degrees Fahrenheit in the summer, when the sun remains out for 24 hours a day. Vinson is part of the Seven Summits, aka the tallest peaks on each continent, and as such has received a high amount of attention and dedication from climbers.

Denali, or Mt. McKinley

Denali, also known as Mt. McKinley and located in Alaska, is the tallest peak in North America. With a success rate of only just over 50%, the mountain is renowned for its difficulty, and it has taken the lives of around 100 climbers. Part of the problem is the incredibly cold weather: unlike the peaks of the Himalayas and Africa, Denali is located very far north of the Equator, meaning that even in July you can see temperatures as cold as -20 degrees Fahrenheit, with windchills below -50 degrees Fahrenheit. One thermometer that was found on the mountain had recorded a temperature of -100 degrees Fahrenheit. But despite these difficulties, the mountain still sees regular and dedicated attempts; as part of the Seven Summits, it is a point of pride for climbers to conquer, and it’s also part of Denali National Park, one of the most beautiful on the continent.