Chavin is a small but fascinating archaeological site in the Andes of central Peru. The Chavin culture is the first major culture of Peru that developed arts and iconography. This iconography thereafter had a big influence way outside the borders of this civilization. As the site is not very vast but well marked, I believe most visits to Chavin are quite similar. Mine was almost exactly what Els and Juha described. I will thus only add some details.
The main difference between my visit and the two exhaustive previous reviews are that I did not use public transportation nor a private driver but a tour company. Chavin is best visited from Huaraz, which is also the main gateway to Huascaran national park WHS. If you only choose day hikes in Huascaran (and not multi-day treks), you better go with tour companies as they are quite cheap, give you a lot of freedom and more reliable than public transport. I thus bargained a package of tours with an operator and included Chavin in it for a good price.
We left in the morning and made a stop en route at Laguna Querococha. It is located in a very beautiful mountain setting and was my first sight of Huascaran. I chose Chavin as my first activity in this region because it lies at a lower altitude and is less strenuous than most hikes. I think it is a good strategy to facilitate acclimatization and avoid altitude sickness. Our guide also showed us the fault in the mountain above the lake that has the shape of Peru on the map.
The guide, only speaking spanish (I was actually the only non-native spanish speaker in the group), was very interesting and knowledgeable. He sometime works with students and archaeologists of Stanford University investigating the place in winter. As described by other reviewers, we first saw the back of the temples, walked to the main square (Plaza Mayor) and then reached the main temple (Edificio A), passing la Escalinata Blanca y Negra and la Plaza Circular. The external remains are interesting but not overwhelming. However, the underground galleries and chambers are the fascinating gem of this site. The Lanzón, sadly, is not easy to appreciate at its full value in there. The replica at the museum gives a better idea of the grandeur of this stela. We finished with the last Cabeza clava remaining here. The important collection at the museum is more interesting.
Even though Chavin is not as impressive as other precolonial archaeological sites, it makes a very interesting day trip from Huaraz and is a good solution for acclimatization. Learning about early Peruvian civilizations in the Andes was fascinating.