The answer lies in what the building is made of – Portland stone, a type of limestone from the Isle of Portland in Dorset. Portland stone dates from the Jurassic Period of around 150 million years ago. The shells in the walls here are fossils.
Most limestone, including Portland stone, was created by a chemical reaction in warm water. In the Jurassic Period the land that made up Britain was under a warm shallow sea. As sea water heated up from the sun's rays, carbon dioxide gas was released into the atmosphere.
This allowed a sticky substance called calcium carbonate to build up on the sea bed, like scale in a kettle. Sand and dead sea creatures were slowly covered in billions of the sticky particles, which gradually cemented together in layers to form limestone.
The reason fossils from Dorset have ended up here is because Portland stone is a popular building material in London. The stone is very strong and resists weathering. First quarried by the Romans, Portland stone was shipped to London from the 14th century.
It became very fashionable after the Great Fire of 1666, when Christopher Wren used nearly a million cubic feet of it to rebuild St Paul’s Cathedral. The area around Green Park has many Portland stone buildings, so the station reflects the local environment. It is also a reminder of another, much older landscape.
Most Portland stone used for building is carefully finished so that blemishes (including fossils) don’t show. The station by contrast, offers a reminder of London’s development; the ‘modern’ stone city was built from prehistoric sea creatures.
Just behind the station look in the park for a large circular air duct, also made in Portland stone.
Many of the fossil holes have filled with greenery. Sea shells from 150 million years ago have provided a home for new life.
Portland stone features in many London landmarks including; the British Museum, Bank of England, National Gallery, the Cenotaph, BBC Broadcasting House and nearby Buckingham Palace. It is also used in countless private buildings.
Why not see how many you can find?
Located between Mayfair and the West End, Green Park is one of London Underground’s busiest stations. Over 35 million people pass through it each year.
Ignore the crowds and traffic for a moment though and take a good look at the walls.
Spanning the centre is a decorative frieze of sea creatures. The bricks above and below are covered in strange marks, cuts and holes - including some that look like shells.
| Location: | Green Park London Underground station, City of Westminster, London W1J 9DZ |
| Grid reference: | TQ 28993 80269 |
| Keep an eye out for: | Other buildings nearby with fossils in the walls |
Thank you to -
Rory Walsh for creating and photographing this viewpoint
Dudley Museum and Art Gallery for the illustration of Jurassic sea creatures
“Fossils swim through through ocean beds of Portland stone churches and encrust the statues of proud dignitaries” - Iain Sinclair