The first 12 World Heritage sites, listed in 1978, covered seven countries and included the Galapagos Islands, the rock-hewn churches of Lalibela in Ethiopia and the slave-trading island of Goree in Senegal.

Prague: City of "outstanding universal value"

There are now 506 sites scattered over 107 countries.

Towns on the list include Avignon, Prague, the Vatican City, Old Havana and the kasbah in Algiers. Even the Nazi concentration camp site at Auschwitz in Poland is listed. Famous tourist attractions such as the Taj Mahal, the Pyramids and the palace of Versailles are also listed.

Britain ratified the convention in 1984 and submitted its first list of candidates for World Heritage status in 1986.

It is the fifth largest contributor to the World Heritage Fund which has an annual budget of £2m.

Around 25 sites have just been put forward by the UK for World Heritage status. The title is largely symbolic but some sites can secure grants.

Stonehenge, for example, has been awarded around £125m to improve roads and visitor facilities.

But the UK Culture Secretary Chris Smith would like to see a change in the system to provide more help to preserve the sites.

"In each of the world heritage sites you need now to bring forward a comprehensive management plan of how the governments and the local authorities that own the sites are together going to manage the sites, protect them for the future, conserve what is best about them," he said.

There are 17 buildings and towns in the UK already listed as World Heritage sites. They are:

• Durham Cathedral and Castle
• Fountains Abbey, St Mary's Church and Studley Royal Park
• Ironbridge Gorge
• Stonehenge, Avebury and associated sites
• Blenheim Palace and Park
• The Palace of Westminster, St Margaret's Church and Westminster Abbey
• The city of Bath
• Hadrian's Wall military zone
• The Tower of London
• Canterbury Cathedral
• The castles and town walls in Harlech, Beaumaris, Caernarfon and Conwy in Gwynedd
• St Kilda
• Giant's Causeway and Causeway coast
• Henderson Island, South Pacific Ocean
• Edinburgh Old and New Towns
• Gough Island Wildlife Reserve, South Atlantic Ocean
• Maritime Greenwich.