Human nature's versatility is evident in their ability to survive in some of the most hospitable and remote places on Earth. What's more is that humans don't just survive but often flourish in these settlements, so it's no wonder that vast, sprawling cities and bustling trading villages can be found in the world's highest peaks and valleys.
Here are seven of the highest cities on the planet, some of which have become capitals of their country, some long abandoned and left to the elements.
1. The Bolivian city of Potosí is reportedly the highest city in the world, sitting at 4,090 m (13,420 ft) above sea level. The peak of Cerro de Potosí, or Cerro Rico – Rich Mountain, dominates the city's skyline, and towers a further 800 m above the rooftops.
2. Sitting at 2,850 m above sea level and around 22 km from the equator is the Ecuadorian city of Quito. It is flanked either side by the Andes, and on a clear day it's possible to see the snowcapped volcano, Cotopaxi in the distance.
3. Close to the Tibetan border, 12,630 ft high above sea level is the small secluded town of Laya. It is one of the most remote towns in Bhutan, so remote that routes to the area are often closed or impassable over the winter months.
4. It's hard to believe the area around the towering peaks of the Atakor Mountains are populated; the area is so dry and desolate. But even here life goes on, in a city located around 2,728 m above sea level, called Assekrem. The city lies on one of the oldest trade routes through the Sahara.
5. La Paz, also in Bolivia, is a sprawling city 3,500 m above sea level and home to just under one million people. It's in a great position for those who want to spend some time visiting a number of sights at altitude – the old ruins of Tiahuanacu are nearby (much older than Machu Picchu), as is Lake Titicaca.
6. The tiny Principality of Andorra is a small landlocked country nestled in the Pyrenees mountain range, between Spain and France. The whole country is no bigger than 470 sq km (181 sq m) and the highest of the peaks – Coma Pedrosa – is 2,946 m (9,665 ft) above sea level. It's also one of Europe's most popular ski destinations.
7. No list about cities in the clouds could be complete without the ancient city of Machu Picchu, high in the Andes. Thought to be built between 1460 and 1470 AD, the city sits at 2,430 m above sea-level and is often covered in cloud. The UNESCO World Heritage Site is popular with trekkers, some would say almost too popular.