Abstract: A tower segment, in particular for a tower of a wind power installation, to a tower, in particular a tower of a wind power installation, to a wind power installation and to a method for constructing a tower. In particular, the invention relates to a tower segment, in particular for a tower of a wind power installation, for attaching to a support structure, in particular to a foundation, comprising a tower base element having an upper end and a lower end, and a threaded opening arranged at the lower end, a flange, which is arranged at the lower end, having a first flange opening and a second flange opening, wherein the tower base element and the flange are connected by a fastening element arranged in the threaded opening and the first flange opening, and wherein the second flange opening is formed in such a way that a connecting element of the support structure can extend through the second flange opening.