Firstly, and unlike the other rides on this web site, Paris-Brest-Paris is NOT a route I developed myself. It is a 1200km cycling event organised by the Audax Club Parisien, that takes place every four years. I rode Paris-Brest-Paris in 2019 and this is a link to my story of the experience.
Since 2017, I have been getting in to audax rides as a natural development of my interest in long bike rides. Benefits include lots of pre-existing routes and a friendly community of like-minded cyclists. The website of Audax UK (the long distance cyclists’ association) is the best place to start learning about the world of audax.