The ruins of Chavin de Huantar are amazing. According to the guide, the society of Chavin de Huantar was obsessed with the number 7. The main plaza measures 49 meters by 49 meters (perfect square of 7). Apparently, they got to measure the size of the Earth and from there calculated a measuring unit identical to the meter. I noticed that the plaza and the main temple are perfectly aligned to the north and south on each side. There are several interesting galleries and labyrinths on site as well. Additionally, there is an altar stone that has perfect correlations with the Orion Constallation. In it, the high priests viewed the constalation reflected in the water filled holes in the rock.
For those with claustrophobia, may I suggest a nap for a few hours later we passed through the Cauisin tunnel at 4550 meters above sea level. It's not that long, but since it was constructed at such a high elevation is probably one of the highest tunnels of its kind in the world.
As you can see from the picture, there is a Natural Map of Peru on the mountain side a few meters past the Laguna Querococha.
I took a tour from Huaraz to Chavin de Huantar. I can't remember the exact price, but judging on how low my budget in Peru was at the time I reckon it was for under $20 USD for the whole day, maybe less. Trust me, it's worth every penny!