A memory palace, also called a method of loci, was a mnemonic system used for complex memorization in the days before external memory devices were common.
If you couldn’t write something complicated down, how were you going to remember all the details? A memory palace mentally pairs rooms in the imaginary palace with segments of the material to remember. Often the best mental memory palaces are based on an actual physical place.
If you want to try to construct a memory palace to help remember something complicated, here are some instructions for going about it.