One is his increasing use of gradations of colour and light (colour modulation), including sfumato, often achieved by tonalism, to define the shapes of figures and landscapes and to create an atmosphere wherein all components of the painting are unified. Some believe he may have been taught this by Leonardo da Vinci, who is said to have visited Venice in 1501. In his "Castelfranco Madonna", 1505, the use of line and colour modulation are equally balanced but in "The Tempest", c.1510, colour modulation almost entirely replaces line creating an artistic vision in which humankind and nature are combined. Some consider the "Tempest" one of the most important paintings produced in Italy as the components are held together by colour and there is a dreamy atmosphere of perfect harmony. Giorgione was the first painter to assign a leading role to nature and whenever his paintings feature a landscape it becomes an integral part of the painting.