A post-tensioned precast segmental concrete tower has a stack of annular segments with uniform cross-sections which varies over the tower height. The transition between tower segments occurs in stages and is achieved using annular members or segments which support and anchor post-tensioning tendons that transfer loads passing through the tower as a result of a change in tower geometry. The tower segments are match cast against one another in fabrication to create tight matching opposing surfaces when placed into the tower and to create tight joints. The match casting eliminates the need for grout between precast segments, resulting in a faster tower erection time and high durability of the joints. All annular segments have horizontal joints and no vertical joints. The tower geometry simplifies the formwork system used to precast the segments, and the post-tensioning tendons tie all segments together and to the foundation.