Factbox: Five facts about the Shanghai World Expo

(Reuters) - Here are five facts about the Shanghai World Expo taking place between April 30 and Oct 31.

* China says it has spent $4.2 billion -- double what it spent at the Beijing Olympics -- to host the world's largest exhibition fair. It is the most expensive Expo to date and local media have reported the true cost is closer to $58 billion.

* The size of the Expo site is twice the size of Monaco and 20 times bigger than the last World Expo held in Spain's Zaragoza in 2008. The site spans 5.3 square kilometres across both sides of Shanghai's murky Huangpu River.

* Shanghai allocated $45 billion to upgrade the city's infrastructure, creating the world's longest metro system, two new airport terminals and a $700 million promenade on the historic Bund as well as new roads, parks and bridges.

* Shanghai expects 70 million visitors will attend the Expo, though just 5 percent will be foreigners. The city has dramatically increased security measures with bag checks at every subway station and bomb-recognition pamphlets distributed to offices in the Pudong financial district.

* The Shanghai Expo is promoting itself as the first green and environmentally friendly Expo, creating China's largest solar plant as part of the facilities and using zero emission vehicles for transportation. But most of the exhibition sites will be demolished when the Expo ends.

(Writing by Farah Master; Editing by Ben Blanchard and Sanjeev Miglani)