Ancient Ruins and Archaeology is a 1964 science book by L. Sprague de Camp and Catherine Crook de Camp, one of their most popular works. It was first published by Doubleday and has been reprinted numerous times by other publishers. Paperback editions since 1972 have generally reverted to the title Citadels of Mystery, which was the de Camps' original working title. Translations into French, German and Portuguese have also appeared.