In the dry hills of the Cordillera Negra [1] and the steep valleys of the Cordillera Blanca [2], there are plenty of options for good day hikes. A 40-minute taxi drive will drop you at the start of the trail, and hikes can range 2–9 hours in length.
In both ranges, the trails fade in and out of grasses, and can be a challenge to follow, but with a guide or an adventurous spirit and an early start, you can easily make it to your destination and back in one day.
The Casa de Guías (Parque Ginebra 28-G, tel. 043/42-7545, agmp [at] casadeguias [dot] com [dot] pe, www.casadeguias.com.pe [3], 8 a.m.–1 p.m. and 4–8 p.m. Mon.–Sat., open Sun. during high season) can provide good maps and trail information; Michel Burger, the French owner of Pérou Voyages (Julián Morales 823, tel. 043/42-6249, www.perouvoyages.com [4]), has spent many weekend mornings scoping out trails. Michel, who speaks French, Spanish, and German, is happy to guide or give information about hikes.
Links:
[1] http://www.moon.com/destinations/peru/huaraz-and-the-cordillera-blanca/trekking-the-andes/cordillera-negra
[2] http://www.moon.com/destinations/peru/huaraz-and-the-cordillera-blanca/trekking-the-andes/cordillera-blanca
[3] http://www.casadeguias.com.pe
[4] http://www.perouvoyages.com