Water tank branch canal, Cape Verde © UNESCO - D. Roger

Water is one of the most versatile elements on Earth. It can change in a matter of minutes from liquid to steam, from ice to liquid.

Three of the world's most important rivers - the Nile, the Amazon, and the Yangtze - are each more than 6,000 km long. Eighty percent of the Earth's surface is covered by water: through sheer necessity, therefore, many of the world's greatest discoveries have been accomplished by the means of water. Rivers, seas, lakes - these are the waters that connect us all and have allowed us to expand our horizons, both geographical and cultural.

When roads were all but unheard of, inland travel was mainly done by water. Great urban centres throughout the world, for instance, were the seat of intense commercial and cultural exchange, bringing new languages, beliefs, traditions, literature, and products into the various cities with which contact was made. Waterways have, through commerce and the trade of goods and services, been a motor for cultural change and exchange

In addition to offering a route on which to transport products, people and cultural values, such as language and traditions, water also provides the primary element of technological development. It is the first recorded source of energy, produced through the use of watermills as early as the first century BC in the Roman Empire.