Lima itself is dotted with excavations of pre-columbian cultures, but in Pachacámac, about 18 miles/30 km SE of the capital, the ruins literally spill out of the sandy hills above the ocean. I visited mid-week--there seemed to be more archaeologists than tourists. Temples and tombs cause archaeologists to continually push back the date for the origins of civilization in this part of South America. (Well before the Inca, many cultures built cities and irrigation canals--some may be contemporary with the ancient societies of Mesopotamia!)
Pachacámac is one of the easiest-to-get-to locations to visit and learn more about these pre-Inca societies. On a quiet mid-week visit, it's sobering to wander the ruins of was once a vibrant complex...
The Incan archaeological site of Pachacamac is a former citadel sitting about 31 kilometers (19 miles) from the city center. While it can appear to be little more than a whole lot of sand and dust in parts, excavations have revealed a few of the main temples among the rubble. From the top of the Sun Temple (Templo del Sol), expansive views encompass Lima and the coast; and the Palacio de Las Mamacuna (House of the Chosen Women) features remarkable Inca-style trapezoidal doorways.
We negotiated a day rate to explore with our driver and he took us out to the ruins where we hired a guide/historian to explain what we were seeing.
The ruins, which are still not completely unearthed due to funding issues, include a number of temples used by the Incas and pre-Incan civilizations dating back to 200 AD. If you're looking for a day trip that takes you outside of Lima, this is a good way to spend a half of a day. The guide is a must to have any understanding of what you're seeing. Plus, the drive from Lima's city center to Pachacamac, littered with shantytowns, is an eye-opening one.