“The main dinner course was just being served in the massive, ancient Greek hall when the expansive ceiling collapsed, crushing every one of the many guests in their seats. Not a single attendee survived, except for the poet Simonides, who had left the room just before the tragedy. In the days that followed, workers who lifted the heavy rubble found that the victims were so horribly disfigured that they were impossible to identify. But Simonides was able to help. By mentally walking alongside the long table, he found he could reconstruct which guest had been sitting in which place. Based on where the bodies lay, he named each one of the deceased.”

You can read about a  very powerful memory technique, called loci method or memory palace, that requires training and has been used since classic Greece. Maybe the Oldest Brain Fitness Program.

Great Wikipedia entry, too.