Tarzan and the Forbidden City is a novel written by Edgar Rice Burroughs, the twentieth in his series of books about the title character Tarzan.
A young man named Brian Gregory has disappeared in Africa, looking for the fabled Father of Diamonds; his father and sister want to go rescue him, and they can only enlist Tarzan's help because they know Captain Paul D`Arnot. By chance, Tarzan and Brian are lookalike, thus making some vile scoundrels to think Tarzan is Brian. They are also heading out after the big old diamond.<br>The Forbidden city is again in a secret valley, with two cities Ashair and Thobos in war, because of the Father of Diamonds.Tarzan has to fight many times against different foes, once even a mansize unicorn seahorse!<!-- unicorn not mentioned, but book says seahorse has single horn, thus unicorn. R-59.-->
The book has been adapted into comic form by Gold Key Comics in Tarzan nos. 190-191, dated October-November 1970.