Ironbridge, United Kingdom
Domestic Visitors: 940,000
International Visitors: 60,000
Total Visitors: 1,000,000 (2017)
Ironbridge Gorge is the six square miles that changed the world.
It is "of universal significance for its unique role in the development of the Industrial Revolution that largely originated in Britain in the 18th century and later spread across the world."
Ironbridge was "inscribed onto the UNESCO World Heritage List in 1986 and has been hailed at the second most highly recommended World Heritage Site by contributors to the travel critique website Tripadvisor."
(quotes from the 2017 Ironbridge Gorge World Heritage Site Management Plan)