Bollenstreek or Dutch flower strip is an area stretching 20 miles between the towns of Haaelm and Leiden, where the famous Dutch tulips grow. Holland produces 70 per cent of the world's commercial flower output, and the colorful fields spread as far as the eye can see. Flowers bloom in January, but the best time to visit is from March to April, when the tulip festival takes place. Keukenhof Gardens, the world's largest flower garden, is another attraction with a jaw-dropping 7 million bulbs on bloom on 80 colourful acres.