Which World's Fair/Expo had the largest attendance?

The Expo 2010 Shanghai China, was held on both banks of the Huangpu River in Shanghai, China, from 1 May to 31 October 2010. It was a major World Expo in the tradition of international fairs and expositions, the first since 2005. The theme of the exposition was "Better City – Better Life" and signifies Shanghai's new status in the 21st century as the "next great world city".

It was the most expensive Expo in the history of the world's fairs. The Shanghai World Expo was also the largest World's Fair site ever at 5.28 square km (2.039 square mi).

The Expo introduced numerous urban best practices and concepts from all over the world which the organisers hope will be a lasting legacy for better urban life in China and around the world. It advocated for future development to focus on environmental sustainability, efficiency and diversity. The innovations and achievements of the event were summarised in the Shanghai Declaration issued by the participants of the Expo. United Nations Secretary-General Ban Ki-moon stated at the closing of the Expo, "Thanks to this Expo, millions of people learned about possibilities for making our cities healthier and safer, cities that better integrate nature and technology, cities that offer their citizens cleaner air and water, and better lives all around".

By the end of the expo, over 73 million people had visited – a record attendance – and 246 countries and international organizations had participated.