I went to Caral today. The Sacred City of Caral is some 200 km north of Lima. It is the most ancient city of the Americas, inhabited between roughly 2600 BCE and 2000 BCE, and is a well-studied site of the Caral civilization.
Since I live in Miraflores, a southern district of Lima, I had to drive across all the city to get the (north)Panamerica highway. Good to go on sunday since traffic is not so heavy.
There are other archeological sites from the same civilization in the northern valleys of Lima region, like Bandurria. However Caral is the best mantained site, and the most interesting. Since it's like 3 hours from Lima, visiting other sites requires 2 days (Bandurria and Caral may be visited in one day, but it's too rush. I strongly recommend to spend a weekend. If you go in summer you can combine it with beaches and swimming, though the heat in Caral may be too strong.
The whole Caral city contains around 19 pyramid complexes, but the best restored that conform the circuit are around 5. It's better to visit the site in winter or spring, cause in summer is very hot and the sun is very intense. The pyramids are not within the green fields of the valley, but in the sand near the arid hills.
For people who like history and archeological sites, Caral is a must. It is far more interest that the huacas within Lima, but of course the tour is not as exciting as the Cusco tours (the Inca buildings are from S. XV, so they are in better shape, besides the Incas got more "technology"). And the tour also gives you the opportunity of see more of the peruvian coast geography and its towns, its valleys, and enjoy the seafood.