The high Andes are one of the most inhospitable places on Earth.
Miners crawl through tunnels in the glacier to mine gold
There is precious little oxygen to breathe, and the temperature rarely rises far above freezing. Yet in this bleak, forbidding place there is a town with 20,000 inhabitants.
For 500 years, the lure of gold has drawn people to Rinconada. First came the Incas and then the Spanish.
Prospectors still endure the high altitude and harsh weather in the hope of striking lucky in the state-owned gold mine.
But instead of El Dorado, they find a town of broken dreams.
Five and a half kilometres above sea level, Rinconada is the highest shantytown in the world. Rinconada - which means corner in Spanish - has become a hideout for the desperate and those on the run from the authorities.
In this town there is no drinking water, there are no toilets and no sewers - just an open trench in the middle of the main road where the rubbish and excrement is deposited in the open air. The smell is unbearable.
The situation is now so bad that some observers say the drinking water of over one million people is threatened with contamination.
The issue is featured in Slum At The Summit, a film in the Earth Report series made by TVE and shown on BBC News 24, BBC One and BBC World.
The trench at Rinconada can only absorb a tiny proportion of the town's rubbish. The majority is dumped between the houses or in the immediate surroundings of the town.
The excrement and rubbish has been piling up day after day, around the houses for dozens of years. Disease is commonplace, especially among children.
Assisted by two nurses and a midwife, Hernán Ventura Chambilla is the only doctor in Rinconada.
"The population of Rinconada is, without a doubt, the urban population living at the highest altitude in the world," he tells TVE.
"Unfortunately, this population lives in the middle of its own excrement and rubbish. It's incredible, but everything is dumped anywhere at all, out in the open.
This small medical team treats over a thousand patients a month.
Rubbish not dumped in the trench is deposited around the town
"Most of the children under five in Rinconada suffer from lung infections and diarrhoea. You don't have to look very far to work out the reasons for these illnesses: the altitude, the climate and the polluted environment these children live in are the causes," Dr Chambilla explains.
"Thanks to God, the town is covered with snow nearly all year round and the cold slows down the spread of epidemics."
The snow piles up on the heaps of rubbish and excrement. When the snow melts, it forms polluted streams that run into the lake and river at the outfall of the glacier.
In days gone by, the lake was considered a source of pure water. But today it carries the pollution from Rinconada downstream. The mine pollutes the Rio Carabaya which, after travelling 250 km, flows into Lake Titicaca.
The authorities seem to think that small-scale mines only cause local pollution. In fact, small-scale mines are having an impact on the ecosystem of the entire country.
Mines throughout Peru release 100 tonnes of mercury each year; 80 tonnes in liquid form and 20 in gas. According to the Ibero-American Programme for Science and Technology in Development (Cyted), most of the main rivers in the south of Peru are contaminated by mercury. As yet, there is no official record of contamination levels.
At the end of the 1980s, Peru experienced an economic crisis. In the five years between 1984 and 1989, inflation reached 7,000,000%.
Most children under five suffer lung infections and diarrhoea
The recovery has been painfully slow. Qualifications are no guarantee of a job. Larger families cannot support themselves on subsistence farming - which is why some people are prepared to endure the squalor of life in Rinconada.
Miner Rodolfo Nina Choque came to the town in 1998.
"There are so many problems [in Peru]. We study, get qualifications and become good professionals. Then, at the end of the day, there's no work - only unemployment. So, the only way to find work is to come here, to the mine," he tells TVE.
"God willing, we'll find enough gold and be able to leave and do something else, open a little shop or find another job - a job less difficult, less tiring."
The whole town is afflicted by gold fever. The gold is found in thin seams under the glacier and in the mountains, making it very difficult to extract.
This job cannot be carried out by machines; only by men crawling through the darkness. The profits to be had are as slender as the seams themselves.
The mountain and all its resources belong to the State of Peru, which rents it out to a mining company, the Corporación Minera Ananea.
The company sub-contracts to some 300 small contractors who, with a limited surface area, are only able to excavate a few mine shafts. The miners are hired according to the "cachorreo", a verbal contract by which the miners work for free for the contractors for a month.
The trench can only absorb a tiny amount of the town's rubbish
After 30 days of unpaid work, the miners are allowed to work the mine for their own profit for a single day. It is a cruel lottery. If the seam is good, the miners can survive the following month, perhaps even save a bit.
But if the seam is poor, the miners have to borrow or go without some of their food. For 95% of the people living here, the average income is between US$40 and US$100 a month.
When the miners can work for themselves and finally earn a bit of money, in accordance with the "cachorreo", they have to produce a minimum of 5 to 10g of gold in order to survive the following month.
Rodolfo Nina's day starts at six in the morning with the walk up to the mine. It will take him an hour. When he gets to the mine, the overseer hands out the coca leaves. Chewing them numbs the body - there could be no mining without it.
An offering to the mine itself is made before going down the shaft, a few coca leaves slid under a stone, so that the yield is generous.
Food or a bottle of alcohol could also be given as offerings. A belief dating back to Inca times claims that leaving a human brain to rot inside the mine causes a chemical reaction which makes gold come to the surface of the rocks.
This belief still has its followers in Rinconada, and the last human sacrifice recorded by the Police Commissioner dates only to March 2003.
Inhabitants have no other option for disposing of waste
Dynamite is used to blast the tunnels. There is no remote-controlled electronic ignition here. The fuse is lit and the miners run as fast and as far as possible. Accidents are inevitable.
The ore that is extracted from the seam is crushed to powder. This is the preparation for the next stage, during which the gold is separated from the rock. The gold is separated from the ore using a "quimbalete", a big circular stone used like a grindstone.
Water is poured into the bowl of the quimbalete, followed by mercury. The powdered ore, containing gold, is added to the water.
As a result of the to and fro motion of the stone, the gold fixes itself to the mercury, while the rock powder stays in the water.
Counting the cost
With each movement of the quimbalete, a little water is discarded - water that is contaminated with mercury. Eventually the mercury will find its way into the mountain ecosystem.
Although as much mercury as possible is salvaged, it is estimated that for every tonne of ore, 500g of mercury escapes to contaminate the environment.
At the end of the process, a mixture of gold and mercury is obtained which the miners sell. They will be looking for the best price possible from the town's gold merchants.
The merchant heats the mixture using a blowlamp to evaporate the mercury. This leaves pure gold at the bottom of the saucer. A gram of gold is worth 35 soles - about $10.
After 30 days' unpaid work, miners work for their own profit for one day
The gas comes out through chimneys, directly onto the roofs of houses. In contact with cold air, the mercury condenses and is deposited around the chimneys. Between two and three tonnes of gold a year are produced at Rinconada, releasing four to six tonnes of mercury into the air.
As there is no drinking water Rinconada, the inhabitants collect the melting snow from their roofs and use it for their personal consumption.
The mercury is ingested directly by the miners and their families. The metal attacks the nervous system; commonly making people more aggressive and leading to serious problems in limbs and internal organs. It may be one reason for the appalling levels of domestic violence in Rinconada.
Throughout Peru there are roughly 40,000 miners working in small-scale mines. They extract 22-and-a-half tonnes of gold a year, around a quarter of Peru's total gold production. It earns the country about US$200 million in foreign currency.
Yet neither the miners nor the contractors have any kind of legal existence. They receive no government aid, are not entitled to social security and are not allowed to borrow money for investment.
A nationwide campaign is now under way, led by NGOs such as the Gama Project, to get the authorities to give legal status to the small-scale mines - and to take measures to control pollution.
"If only it were possible to provide this population with a water treatment centre and distribution network, and to also have drains, a waste disposal centre and a rubbish collection service," Dr Chambilla tells TVE.
Rinconada is a bleak, forbidding spot
"With all that, I'm sure that we could reduce the number of illnesses here."
Rodolfo Choque thinks an even simpler change would make things easier on the town's inhabitants.
"The road should be tarred to make transport easier and waste less time. That would improve trade and commerce and would help us to increase our income. Now that would change our lives," he says.