Anchor cage for a foundation of a wind turbine. The anchor cage comprises at least an upper load distribution plate (1), at least a lower load distribution plate (2), and a plurality of first reinforcement elements (3) extending between said plates (1, 2). It further comprises at least one intermediate load distribution plate (4) placed between the upper load distribution plate (1) and the lower load distribution plate (2), and a plurality of second reinforcement elements (5) extending between the upper load distribution plate (1) and the intermediate load distribution plate (4), and being shorter than the first reinforcement elements (3). An assembly method for the anchor cage is also described. A foundation is also provided in which the total post-tensioning value provided in the upper part of the foundation (6) is different from the total post-tensioning value provided in the lower part of the foundation (7).