WHY: Lavished with dreamy canals and storybook buildings, Amsterdam is always a looker, but spring heralds a particularly sensational colour palette as millions of trees and flowers radiate in and around the city. Tulips are the big draw, but there are other botanical surprises - and you'll want to ensure there's ample storage space on your camera. HOW: Tulip mania first struck here in the 17th century after these exotic plants arrived from Asia, sparking phenomenal interest and demand. The Dutch appetite for tulips endures with festivals and flower parades. April is usually the peak - when tulips colour almost...