Walk out to the very tip of the island and the land runs out beneath a red-and-white tower, while off the point the sea itself seems to boil, a churning tide-race where currents meet and fight. This is Portland Bill, the southern nose of a great tilted slab of stone thrust into the English Channel. Behind you stretch the quarries that gave the world one of its most famous building stones. Ahead, only the racing water and the wide grey Channel.
The Isle of Portland is really one enormous block of Jurassic limestone, tilting gently to the south, tied to the mainland only by the long shingle causeway of Chesil Beach. That limestone was laid down in a warm sea around a hundred and forty-five million years ago, and it is superb stuff to build with: pale, even, and durable.
Men have quarried it since at least Roman times, but its great fame came after the Great Fire of London in 1666, when Sir Christopher Wren chose Portland stone to rebuild St Paul's Cathedral. From that moment the island's stone travelled the world. It faces the Cenotaph in Whitehall, the headquarters of the United Nations in New York, and countless buildings between.
Guarding the calmer harbour side stands Portland Castle, built by Henry the Eighth in 1540, while at the wild southern tip the lighthouse warns ships off the deadly race. There has been a light here since 1716; the present bold red-and-white tower dates from 1906.
Look first at that lighthouse and, beyond it, the tide-race churning off the Bill, one of the most dangerous stretches of water on the whole south coast. Look second at Pulpit Rock, the dramatic leaning sea stack near the point, a great slab of stone propped against the cliff like a book on a lectern.
Look third at the old quarries inland, deep workings where the famous white beds lie bare and you can read the layers of the stone straight from the rock face. Look fourth, in spring and autumn, to the skies and cliffs, for Portland is a celebrated migration watchpoint with its own bird observatory, and puffins nest on some of the ledges.
And look fifth, among the quarry grassland and stone, for rare flowers and butterflies, including the Portland sea-lavender that grows nowhere else on Earth.
The stone is the island's whole story, and the best way to feel it is to stand in St Paul's Cathedral in your mind's eye and know that it came from here. Picture the quarrymen levering great pale blocks from these southern cliffs, three centuries ago, and loading them onto ships to be carried up the coast and worked into Wren's mighty dome.
From this exposed, wind-scoured slab of rock at the edge of the Channel came the stone for cathedrals, war memorials and parliaments across the world. The island is small and hard and battered by the sea, yet its bones stand tall in the greatest buildings of the age.
A word of care, and it is a serious one here. The tidal race off the Bill is genuinely dangerous and no place to venture near the water. The quarry cliffs are sheer and the sea cliffs unfenced, so keep well back from every edge, and never climb on the crumbling faces. Give the racing water and the drops the wide berth they demand.
The circuit of Portland is an optional loop off the main Coast Path, and a fine one, but allow most of a day for it, for the island is bigger and wilder than it looks. When you have seen the lighthouse, Pulpit Rock and the old quarries, take a last look at the tide-race off the Bill and think of the pale stone beneath your boots, standing in St Paul's and the Cenotaph and half the great buildings of the world. Then turn back along the cliffs. Walk safe.
