Method for installing an offshore structure at an offshore site having a sea bottom and a water depth defining a sea level; the offshore structure including a seabed fixation structure, a transition piece and a superstructure; the method comprising installing the seabed fixation structure to the sea bottom, such that the seabed fixation structure at least partly extends above the sea bottom; positioning the transition piece on the seabed fixation structure, wherein at least an upper side of the transition piece is above the sea level; positioning the superstructure on the transition piece such that the superstructure is extending above the sea level; wherein the connection between the transition piece and the seabed fixation structure and the connection between the transition piece and the superstructure is provided as an in-line connection comprising multiple sets of conical rings engaging each other; wherein at least one of the in-line connections is at least partly below the sea level.