Egyptologist Mark Lehner thinks it took almost 20,000 people to build the Great Pyramids. But where did all those workers live? In this podcast, Lehner describes how he found evidence of a "lost city" on the Giza plateau.Podcast produced by David Levin. Original interview by Peter Tyson. Music courtesy Pharaoh's Daughter (freemusicarchive.org/music/Pharaohs_Daughter/), Selva de Mar (freemusicarchive.org/music/Selva_de_Mar/), and APMmusic. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers.To learn more, go to pbs.org/nova/sphinx