Elizabeth Bathory is one of the world's least known killers. Over the course of many years it is estimated she killed over 600 young girls. She did this to be eternally young. She felt that by using their blood she would be beautiful and never grow old. (See 100 Tyrants for more information)
After the news of her murders came out -- and this was only after she began to kill young noblewomen -- she was walled up in her castle. Later this castle fell into ruin, and it has not been restored. It is located in a park with many endangered plants growing around it. It is now found in Slovakia.
made into a book in more recent years, Dracula the Undead, and Bathory is one of the main characters. However, as many have said, it is not as good as the original book Dracula. (this is my view as well.)