Aerial image of Silbury Hill, a prehistoric human-made chalk and clay mound near Avebury, UNESCO World Heritage Site, Wiltshire, England, United Kingdom, Europe

Aerial image of West Kennet Long Barrow, a Neolithic tomb or barrow, on a prominent chalk ridge, near Silbury Hill, Avebury, Wiltshire, England, United Kingdom, Europe

Aerial view of Meggs Hill (Gog Magog Downs) (Gog Magog Hills) (the Gogs), a range of low chalk hills, Cambridgeshire, England, United Kingdom, Europe

Aerial image of Westbury chalk quarry, with Westbury White Horse and Bratton Camp Hill Fort in background, Wiltshire, England, United Kingdom, Europe

London City Skyline in autumn seen from Primrose Hill, Chalk Farm, Borough of Camden, London, England, United Kingdom, Europe

A farmer ploughing chalk hills on the East Yorkshire Wolds, Yorkshire, England, United Kingdom, Europe

White horse, the Cherhill Downs, Wiltshire, England, United Kingdom, Europe

Scenic view of white chalk cliffs and green hills along the coastline under a cloudy sky at Seven Sisters, South Downs National Park, East Sussex, England, United Kingdom, Europe

The Ridgeway ancient prehistoric routeway passing across chalk countryside near Hackpen Hill, Wiltshire, England, UK

Cherhill white horse, first cut into chalk downland in 1780, Wiltshire, England, United Kingdom, Europe

Seven Sisters cliffs walk, South Downs National Park, East Sussex, England, United Kingdom

The white cliffs of Seven Sisters, South Downs National Park, East Sussex, England, United Kingdom

Corn fields and rolling chalk hills in mid-summer sunshine near Fridaythorpe on the East Yorkshire Wolds, Yorkshire, England, United Kingdom, Europe

Long Man of Wilmington chalk figure, Wilmington, East Sussex, England, United Kingdom, Europe

Chalk and limestone cliffs between Lulworth and Durdle Door, Isle of Purbeck, Dorset, England, UK

White horse dating from 1812 carved in chalk on Milk Hill, Marlborough Downs, overlooking Vale of Pewsey, Wiltshire, England, United Kingdom, Europe

City skyline in autumn seen from Primrose Hill, Chalk Farm, London Borough of Camden, London, England, United Kingdom, Europe

Cutting through chalk hill for the construction of a new section of the M3 Motorway, Twyford Down, England, United Kingdom, Europe

The Long Man, Wilmington Hill, near Wilmington, South Downs, Sussex, England, United Kingdom, Europe

Dog, Santorini, Greece

Trail through the limestone formations of Castle Hill Limestone Rocks, Kura Tawhiti Conservation Area, Selwyn District, South Island, New Zealand

Limestone formation at the Castle Hill Limestone Rocks, Kura Tawhiti Conservation Area, Selwyn District, South Island, New Zealand

The Jurassic coastline, Dorset, England