A method for up-ending a longitudinal structure, being one of a foundation of an offshore wind turbine or a wind turbine tower to be installed on top of a previously installed foundation, wherein use is made of a crane The method includes providing a longitudinal structure with an upper end and a lower end in a substantially horizontal orientation; connecting the middle hoisting block of three main hoisting systems and one outer hoisting block of the three main hoisting systems to the upper end of the longitudinal structure; connecting another other outer hoisting block of the three main hoisting systems to the lower end of the longitudinal structure; and operating respective winches of the three main hoisting systems until the longitudinal structure is in a substantially vertical orientation with the upper end above the lower end.