Tower segment, in particular for a tower of a wind turbine, comprising: - a casing segment with an inner casing surface, an outer casing surface and a cutout (208, 222) for a door, wherein - the inner casing surface has a first inner reinforcing portion and/or the outer casing surface has an outer reinforcing portion (210, 224), wherein the inner reinforcing portion and/or the outer reinforcing portion (210, 224) adjoins/adjoin the cutout (208, 222), and - the inner reinforcing portion has an inner reinforcing plate and/or the outer reinforcing portion (210, 224) has an outer reinforcing plate (212, 226), wherein - the cutout (208, 222) has a convex upper cutout portion and/or a convex lower cutout portion, and - the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has/have a concave upper plate portion (214, 228, 238) corresponding to the convex upper cutout portion, and/or a concave lower plate portion (216, 230, 240) corresponding to the convex lower cutout portion, and - the cutout (208, 222) has a substantially rectangular cutout middle portion which is preferably arranged between the convex upper cutout portion and the convex lower cutout portion, and - the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has/have a plate middle portion (218, 220, 232, 234, 242, 244), wherein the plate middle portion (218, 220, 232, 234, 242, 244) adjoins the cutout middle portion, wherein - the plate middle portion of the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has at least one middle collar portion (250, 252), characterized in that the at least one middle collar portion (250, 252) is bent over and extends away from the casing segment. - a casing segment with an inner casing surface, an outer casing surface and a cutout (208, 222) for a door, wherein - the inner casing surface has a first inner reinforcing portion and/or the outer casing surface has an outer reinforcing portion (210, 224), wherein the inner reinforcing portion and/or the outer reinforcing portion (210, 224) adjoins/adjoin the cutout (208, 222), and - the inner reinforcing portion has an inner reinforcing plate and/or the outer reinforcing portion (210, 224) has an outer reinforcing plate (212, 226), wherein - the cutout (208, 222) has a convex upper cutout portion and/or a convex lower cutout portion, and - the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has/have a concave upper plate portion (214, 228, 238) corresponding to the convex upper cutout portion, and/or a concave lower plate portion (216, 230, 240) corresponding to the convex lower cutout portion, and - the cutout (208, 222) has a substantially rectangular cutout middle portion which is preferably arranged between the convex upper cutout portion and the convex lower cutout portion, and - the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has/have a plate middle portion (218, 220, 232, 234, 242, 244), wherein the plate middle portion (218, 220, 232, 234, 242, 244) adjoins the cutout middle portion, wherein - the plate middle portion of the inner reinforcing plate and/or the outer reinforcing plate (212, 226) has at least one middle collar portion (250, 252), characterized in that the at least one middle collar portion (250, 252) is bent over and extends away from the casing segment.