In The Library of Babel by Jorge Luis Borges, the speaker describes the Library, as the universe, as
The universe (which others call the Library) is composed of an indefinite and perhaps infinite number of hexagonal galleries, with vast air shafts between, surrounded by very low railings.
This explains how the universe in which the story occurs is made up of hexagons. However, there is also a group of people who believe that the rooms may also be circular as we learn when the speaker says,
The idealists argue that the hexagonal rooms are a necessary from of absolute space or, at least, of our intuition of space. They reason that a triangular or pentagonal room is inconceivable. (The mystics claim that their ecstasy reveals to them a circular chamber containing a great circular book, whose spine is continuous and which follows the complete circle of the walls; but their testimony is suspect; their words, obscure. This cyclical book is God.)
Given that the organization of the library could most likely work with pentagonal rooms, given the vagouness of the specifications. This suggests to me that there is a non-mechanical reason for the choice of the hexagon. So, what is the significance/symbolism of the hexagon?