The Lost City (B4) is a Dungeons & Dragons adventure module by Tom Moldvay. It was first published by TSR in 1982 and was designed as a stand-alone adventure for use with the Dungeons & Dragons Basic Set. The working title for the module was "The Lost City of Cynidicea". Moldvay designed the module as a low-level scenario to give novice Dungeon Masters experience in fleshing out adventures such that it is only partially complete. The plot involves the player characters discovering a ruined subterranean city slowly rising out of the sands. The adventure is set inside a huge step pyramid, with the lower pyramid only sketched out and the city itself described with a list of the major areas and a map. The adventure's main villain is Zargon, a giant one-eyed monster and his minions. The entire double pyramid, not including the city, contains over 100 rooms.