A trip to Saqqara can be easily found from most tour operators in Cairo, especially the one in your hotel, and it is well worth the trip.
Host to some of the world's first pyramids, this site has many step pyramids from the early part of Ancient Egypt.
The site isn't too big, so you can easily walk around it without too much trouble.
Be a little bit careful there - a police officer tried to charge me for walking me round a corner and showing me a fenced up hole in the ground. There is nothing to worry about, just be cautious and you'll be fine.