According to The Writer’s Almanac:
It was on this day in 30 BC that Queen Cleopatra of Egypt killed herself with a snake she had smuggled into her chamber where she was held captive by Octavian, formerly the political rival of her lover Mark Antony. Octavian had defeated Cleopatra and Antony at the Battle of Actium and had taken Cleopatra prisoner. When Cleopatra learned that Octavian planned to parade her as part of his triumphant return to Rome, she planned her own suicide. For centuries, it was assumed that the snake she used was an asp, but it is now thought that the snake was an Egyptian cobra.