The ancient buildings of Caral-Supe really impressed me. This most ancient city in the Americas has a good collection of major structures that are at least partially restored.  The site includes several pyramids, and the biggest of these is quite a sprawling construction with a signature sunken circular plaza in front of it. The Amphitheater (photo) was a unique building, so named because the archaeologists found remains of musical instruments (flutes) in the arena area. Due to their 5000 year age, you aren't allowed to climb on any of the structures, or enter the amphitheater.  There is a nice trail that leads through all the main structures, and there are good signs (English and Spanish) for each major structure. There are also nice signs explaining the culture's origins and spread at the visitor's center.

An impressive feature here is that there are 20+ other smaller sites along the Caral river valley.  You can see one of them across the river from near Caral's main pyramid -- the site is Allpacoto, I believe.    You can catch glimpses of a couple others from the road in along the valley.   View the area with  Google maps satellite view and search for "Arqueologico".  Zooming in can show some outlines of the ruins.

 

I came as a day trip from Lima (rather expensive for Peru at $160) as I was on my own and not otherwise going north of Lima.  The tour included a guide at Caral who wasn't that enthusiastic and seemed to want to cut the tour short if he could. I made it a point to wander on my own to a couple of the parts that the guide seemed determined to skip -- since I had just driven 3 hours to get here, I wanted to fully enjoy the site.  I rather enjoyed the longer walk from the "wet season" parking lot. There's a nice green nature walk for the first part of it, and we saw a couple interesting birds along the way.

On our tour, after visiting Caral, we (there were only 2 of us) were able to convince our driver to visit Vichama instead of going to lunch in Barranca as the tour normally would.  Vichama became the center of the Caral culture around 1800 BC, when Caral itself had declined.  Vichama, on the way back to Lima along the coast, was definitely worth visiting.  It's not as extensively restored as Caral, but archaeologists are actively working there and have made important finds there within the last few years.  One of the finds was a set of relief figures of humans, discovered on an interior layer of one of the temples there. The reliefs alone were worth the stop.

(Word of warning, don't trust google maps to just go to Vichama -- it'll lead you to the backside of the site -- a large sandy hill. You need to search for "Centro de Visitantes Vichama")