Great tridecagram

The great tridecagram is a non-convex polygon with 13 sides. It's created by taking the fourth stellation]] of a tridecagon. A regular great tridecagram has equal sides and equal angles.

It is one of five regular 13-sided star polygons, the other four being the small tridecagram, the tridecagram, the medial tridecagram, and the grand tridecagram.