Location: Dover Date completed: c. 70 Million BC Function: Natural Feature

Think of Britain - and what comes to mind? It could be Big Ben, Buckingham Palace, or your home town - but most likely it would be the White Cliffs of Dover. Before the age of the Jumbo Jet they were the first and last of England that the traveller would see, a highly visible, utterly memorable reminder of home. They face Europe across the narrowest part of the English Channel, a natural route for invaders and migrants since Britain was parted from the continent some 8,000 years ago. However, the cliffs presented a formidable barrier to incomers, so they would have looked for easier landing places along the coast. In 55 BC Julius Caesar commented of the White Cliffs that, "The place was altogether unsuitable for landing" and so landed along the coast at Deal. The Romans built lighthouses, or Pharos, on the cliffs to aid navigation - one of them can be seen today in Dover Castle. In fact, the cliff tops have been fortified since the Iron Age. The Castle dates back to the 11th century, but so strategically vital is its position that it has been almost continuously modernised and fortified right up to World War II. Winston Churchill used rooms in the lower levels as his headquarters during the Battle of Britain.

The White Cliffs were formed around 70 million years ago, when Britain was covered by sea. They are made up of the skeletons of trillions of tiny algae (coccoliths) deposited at the rate of half a millimetre per year to form the white mud and then chalk which makes up the cliffs. Today the cliffs are a popular beauty spot - the area of the South Downs of which they are part has been designated an area of outstanding natural beauty. In 1999 The Gateway, a sustainable National Trust resource for visitors, was built. It provides information on local history, archaeology and landscape, as well as a restaurant.

The White Cliffs have been celebrated in literature, poetry and song, most famously in the song "There'll be bluebirds over the White Cliffs of Dover" (although bluebirds are not, of course, found in Britain).