Where are the world's highest cities?

Despite the lack of oxygen and health risks, high-altitude locations are home to at least 140 million people around the world. From Bolivia’s El Alto to Lhasa in Tibet, what’s urban life like at such dizzying elevations?

At 3,640 metres above sea level, the city of La Paz sits in a canyon resembling something of a bowl within the Bolivian altiplano – a high altitude, windswept plain that dominates the southern and western territory of the country. It’s the world’s highest administrative capital, yet more of the metropolitan population lives in the even higher city of El Alto at 4,150 metres, on the rim of the canyon.

El Alto was uninhabited at the start of the 20th century, but as land became more expensive in neighbouring La Paz, the city grew: for the last 50 years, new development has spiralled out of control into a chaotic mix of winding streets through which water and sewer services struggle to extend.

Yet the indigenous communities at these dizzying heights have benefitted from Bolivia’s recently, rapidly improving economy, an overall reduction in poverty and better integration into Bolivian society. Newfound wealth has seen a boom in the construction of dozens of flashy mansions: these mostly five-storey, mixed-use townhouses – many designed by local starchitect Freddy Mamani – feature futuristic façades plastered in tinted glass and Andean symbols in relief.

Altitude affects every aspect of life in in the conjoined cities of El Alto and La Paz. Even the class structure is based around what elevation someone lives at: the more affluent neighbourhoods are found at the lowest reaches of La Paz, where high-rise condos and gated suburbs sprawl southwest from the city centre. As you move up into the hills, makeshift brick and adobe houses become more common.

City planners in La Paz, of course, needed to keep altitude in consideration when designing a mass transit grid, which is why they installed a $234 million (£140m) cable car system in 2014 to transport residents more than 500 metres between El Alto and the city centre. Known as Mi Teleferico, it’s the longest urban cable car system in the world, and has considerably cut down the time spent in traffic and money spent on fuel.

Tourists visiting La Paz, if walking up to Cerro Cumbre to visit the Mercado de Hechicería (Witches’ Market), will immediately recognise how much more difficult it is to breathe here than at sea level. Every step is a challenge; sleeping becomes difficult too, as do simple bodily functions like digesting food. Some will get soroche, or altitude sickness, with all of its unpleasant symptoms.

“Even cooking at altitude is tricky,” says Kamilla Seidler, head chef of Gustu restaurant in La Paz. “The lack of oxygen affects the rising process in bread making – and our insisting on only using sour dough, not yeast, doesn’t help. Another interesting challenge I found out is that water boils at 86C in La Paz, which means that starch doesn’t really break down, and that rice, potatoes or wheat are generally overcooked on the outside and crunchy on the inside: not nice. So there is a lot of pressure cooking and sous vide going on.”

Despite numerous challenges associated with altitude, humans are able to adapt to lower oxygen levels, both in the short and long term, resulting in settlements with populations that reach into the millions. It is estimated that at least 140 million people in the world live permanently above 2,400 metres. These cities can be found primarily in three mountainous regions: the Himalayas in Asia, the Andes in South America and the Ethiopian Highlands of Africa.

The majority of high altitude cities grow because of an abundance of natural resources, particularly minerals. The economy of the highest permanent settlement in the world, Peru’s La Rinconada (5,100 metres above sea level), revolves around a gold mine. Formerly a simple prospector camp, as the price of gold has risen the population has exploded to around 50,000 people who are all hoping to get rich, despite living conditions that are less than idyllic – with no running water or sewerage system.

While few plants can grow due to the cold temperatures and lack of moisture in many of these locations, the wealth provided from minerals allows these cities to import most food. Bolivia is home to numerous large high altitude mining cities, including Potosí (4,090 metres) and Oruro (3,709 metres), where silver miners are known for chewing bags of coca leaves to keep their energy levels high and curb hunger. Just over the border in Peru are Juliaca and Puno, both above 3,800 metres and with economies related to nearby mines.

One exception is Lhasa in Tibet, sitting 3,650 metres above sea level in the centre of the Tibetan plateau. Surrounding mountains rise as high as 5,500 metres, sheltering the city from the high winds that are found on much of the plateau and creating a moderate microclimate. Although Tibetan royalty were primarily nomadic – moving between summer and winter camps – Lhasa became a semi-permanent royal capital in the 7th century when several Buddhist shrines and temples were built. Similarly, Shigatse (3,836 metres), the second largest city in Tibet, has grown around the Tashilhunpo Monastery, the traditional seat of the Panchen Lama, the second highest ranking Lama after the Dalai Lama.

The sprawling city of Addis Ababa in Ethiopia (2,355 metres, with a population of 3.38 million) is also not based around natural resources; rather it plays an important role geographically. It is located in the physical centre of the country, on the dividing line between two climatic zones, the daga and the wayna daga, which are based on altitude and a natural point of trade.

Altitudes above 1,500 metres begin to have physical effects on humans. When the altitude is high, the air pressure is low, which means that less oxygen is available to breathe. Lungs must work harder to deliver oxygen to the bloodstream. It can take days and even weeks for a body coming from sea level to adjust to high altitude and low air pressure. The higher up one goes, the more intense the effects, which may include altitude sickness and high altitude pulmonary oedema.

Additionally, there are limits to how high an elevation humans are able to survive. The highest permanently tolerable altitude seems to be around 5,950 metres, where a small community of gold miners in northern Chile lived for two years from 1984. If they were any higher for that amount of time, it is likely they would suffer from a gradual physiological deterioration that would eventually be fatal. Himalayan climbers call altitudes above approximately 8,000 metres “death zones”, as most can only survive there for a limited time without oxygen before losing consciousness.

The Altitude Research Centre at the University of Colorado has identified genes that help protect long term high altitude populations against altitude sickness. Compared to humans that acclimatise over time, native populations in these regions are born with better oxygenation, enlarged lung volumes, and have a higher capacity for exercise. A perfect example are the Sherpas of the Tibetan plateau, who tend to thrive even at extreme altitudes above 5,000 metres, which is why they are regularly hired for climbing expeditions.

It’s for this reason that the Ecuador national football team notoriously plays all of its World Cup qualifying games in Quito, at 2,850 metres. While Ecuadorian players are used to playing with the lower amount of oxygen, other teams from the region are not – some say this gives them a significant advantage. After complaints that arose from a series of Brazilian and Argentine losses in Andean venues, there was even a temporary ban by Fifa on international matches at more than 2,500 metres.

There are more examples of benefits for those living at high altitudes. According to a study in the International Journal of Obesity, the higher the altitude one lives at, the lower the obesity rate. The study found Americans living above 1,500 metres to be much less likely to be obese than those living below 500 metres. Comparable studies have found the same results in places like Nepal and Argentina. It’s suggested that low-oxygen environments reduce appetites, potentially because higher altitudes affect hormones like leptin, as well as burn more calories because of increased metabolic demands.

Yet the body adjusting to altitude can go both ways. “As an Andean citizen in Quito (2,850 metres) you always need to plan for time to adapt once you travel to lower elevations,” says Marta Echavarria, a social entrepreneur and co-founder of NGO Canopy Bridge. “Every time I go away for more than three days I have to assume that I will be woozy the first few days I’m back.”

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