Akakor is an alleged ancient underground city somewhere between Brazil and Peru. The German journalist Karl Brugger describes this city in The Chronicle of Akakor (1976) after interviewing Tatunca Nara, a Brazilian Indian. The book is a fact fiction: the interview with Tatunca Nara is the only source and the city is not confirmed separately.
Tantunca Nara speaks about possible contact with extraterrestrials in the ancient past and these extraterrestrials are believed to build this mysterious city. Other two similar cities are mentioned in this book - Akanis and Akahim.