By Martin Vennard
BBC News, Lake Titicaca
Lake Titicaca has a lot to recommend it, but among its most remarkable features are the floating Uros islands.
The 40 or so man-made islands are woven from layers of tortora reeds, which grow on the edges of the giant lake. Titicaca lies 3,800m (12,500 feet) above sea level between Peru and Bolivia.
They are home to several hundred people who are partly descended from the Uro Indians who retreated onto the lake from the Incas, who were the dominant force in the region until the Spanish arrived in the 16th Century.
Though this culture has far outlasted the Inca civilisation, some people are warning that it is now under threat as modern life encroaches.
The Uros are around a 30-minute motorboat ride from the main Peruvian city on the lake, Puno.
The islands are anchored down using ropes attached to wooden poles driven into the bottom of the lake.
In the rainy season from November to February they often move around on the surface of the water. When you walk on them your feet sink down several centimetres.
World's highest lake navigable by ships
3,800m above sea level
15 times the size of Lake Geneva - 190km long and 80km wide
The bigger islands house up to 10 families living in small huts also made from reeds. The smaller ones are around 30 metres in diameter and inhabited by two or three families.
The islanders traditionally lived from fishing, hunting birds and trading with the Aymara people on the mainland.
Over the years, the two peoples intermarried, with the Uros eventually abandoning their own language for Aymara. Now they also make money from the tourists who visit them.
One of the non-native islanders who knows the Uros better than anyone else is Mairo Moya, a 29-year-old Peruvian tourist guide. He came to Puno to study anthropology and spent three months living on the islands.
'Life a struggle'
"What it teaches you is that man can adapt to almost any environment. These people have been here for hundreds of years and they are proud of what they have achieved, literally creating their own land," he explains, sitting with his legs crossed on one of the islands.
"But life is a struggle. The islands rot from the bottom very quickly so new reeds have to be added to the top constantly," Mairo adds. They can last for up to 30 years before a totally new island has to be built.
Life on the islands is ingenious but tough
"The sun is very bright and hot during the day but the nights can be very cold and they have no electricity for heating. Even the most simple of things can be difficult," he says.
They answer calls of nature on smaller islands they have built a short distance from where they live. They dry out solid waste in the sun to avoid polluting the lake, which they also use for drinking water.
"The Uros cook their fish by building fires on piles of stones. They also eat the bottoms of the raw reeds," says Mairo.
"There are no doctors or hospital nearby so people have to rely on themselves. Traditionally, the men help their wives to give birth in their huts."
A missionary school has been set up close to the largest island, Huacavacani, and the children get regular lessons in Aymara. Their religion is a mixture of traditional Indian and Catholic and the Uros bury their dead on the mainland.
Threat to tradition
But what Mairo learnt also worried him. "Many people have moved to the mainland, leaving only a few hundred on the islands. And tourism in the 1980s and 1990s took its toll on the traditional way of life.
"They have no dental care but some of the tourists started giving sweets to the children. The Uros also began to realise that instead of working they could make money by asking the tourists to pay to take their pictures."
Mairo tells all the people he brings to the islands not to give sweets or pay for photos, but to help the Uros by buying their handicrafts, such blankets and knitted finger puppets, and to pay for trips in their reed canoes.
"That way they can maintain their way of life and their dignity," he says.
"Only 10 of the islands allow visitors and it's not too late to preserve what is left of their traditional ways."