But what is sacred geometry?

Recently on the JRE Eric Weinstein & Terrence Howard suggested that the universality of the "flower of life" symbol in disparate cultures around the world may be because it is really a 2D shadow of an nth higher dimensional object....
the E8 root system supposedly creates an 8 dimensional hypercube
the tesseract whilst being made of 8 cubes has always been my starting point for thinking about an extra (fourth) spatial dimension