What was the size of Willy Wonka's factory?

From the text:

One evening, when Charlie went in to see his grandparents, he said to them, 'Is it reallytrue that Wonka's Chocolate Factory is the biggest in the world?'

'True?' cried all four of them at once. 'Of course it's true! Good heavens, didn't you knowthat? It's aboutfiftytimes as big as any other!'