Peru may be known for its cultural World Heritage Sites, but the first site I chose to see upon arriving in country this past October was a natural site: Huascarán National Park. Within hours of landing in Lima, I was on a bus to the lovely small mountain town of Huaraz, and the next day I took the same type of tour as Els to the Lagunas Llanganucos. The mountain scenery was spectacular, and I had an early preview of the park's snow-covered peaks from the breakfast lounge on the top floor of my hotel. Up close on the tour, the mountains were just as impressive, and greener than I expected on the approach to the lakes. Only the lower lake was accessible for the tour, but we had one and a half hours to explore. I opted for a boat tour, then hiked on the walking trails around the lakeshore, in the shadow of Huascarán, the highest peak in Peru. I was hoping to see more Andean wildlife than I saw on my visit to Sangay National Park in Ecuador, but alas, my scorecard stood at: Animals not seen -- spectacled bears, pumas, vicuñas, condors; Animals seen -- ducks and two alpacas hiding amidst the trees. As for flora, even though I didn't see the Queen of the Andes bromeliad on the tour, I did appreciate the Polylepis forest around the lake. I also appreciated the particularly amenable weather, which was very welcome after my misty visit to Sangay. This was a beautiful site!
Logistics: Huascarán National Park can be visited via bus tours, or via private transportation; as Els mentioned, tours to Chavin from Huaraz will pass through another section of the park that is further south than the lakes.