How many days Cairo needs
Three days is a realistic minimum: one for the pyramids, one for the museum, one for Islamic and Coptic Cairo. Four gives you room for Saqqara and Dahshur, which are quieter and older than Giza and which many people prefer.
Cairo is also the standard starting point for a longer Egypt trip rather than a destination on its own. If Luxor or Aswan are in the plan, the transport between them is the thing to get right early.
