Published by Wizards of the Coast.
When one thinks of the greatest city in the history of pulp fantasy, one immediately thinks of the City of the Black Toga, Lankhmar. And when one thinks of the greatest city in the history of fantasy roleplaying, one immediately thinks of Judges Guild’s City State of the Invincible Overlord. First published in 1977, CSIO made a huge splash at the time of its release and it remains, in my opinion, the gold standard for urban sourcebooks over 30 years later.
Read the Full Retrospective/Review at Grognardia.