The best way to enjoy Huancayo [1] is to take a taxi to the east end of Giráldez and walk up Cerrito de la Libertad, which offers nice views over the city and a few stands with comida típica.
From there continue another two kilometers to an odd formation of sandstone towers known as Torre Torre and then traverse the hillside above the city for another few kilometers. The end point is the Parque de la Identidad Huanca, an interesting Gaudí-esque park with curving stone walls, sculptures, and native plants. It is a great evening hangout spot near a range of affordable Peruvian restaurants.
A map of this walk, which takes a few hours, is available through Lucho Hurtado (Giráldez 652, tel. 064/22-3303, www.incasdelperu.org [2]).
There is not much to see in Huancayo [1] itself. The central plaza, Plaza Constitución de Armas, is nondescript, and Huancayo’s churches are all modern, except for La Merced, on the first block of Real, where Peru’s constitution was signed in 1839.
El Museo Salesiano de Ciencias Naturales (Santa Rosa, El Tambo, tel. 064/24-7763, 9 a.m.–1 p.m. daily) has an amazing collection of more than 13,000 Amazon insects, jungle birds, butterflies, fossils, and archaeological artifacts.
Links:
[1] http://www.moon.com/destinations/peru/central-highlands/the-mantaro-valley/huancayo
[2] http://www.incasdelperu.org