This Virtual Tour of the world's largest flower gardens , below some fact 

Keukenhof Garden of Europe (Holland) also known as one of the world's largest flower gardens, in the Netherlands. Keukenhof Park covers an area of 32hectares (79 acres) and approximately 7 million flower bulbs are planted in the gardens annually.
Keukenhof is widely known for its tulips, it also features numerous other flowers, including hyacinths, daffodils, lilies, roses, carnations and irises.