This is a long if relatively easy, well-marked day-hike to Laguna Ahuac (4560m) starting from Huaraz or the Wilkahuaín ruins. From Huaraz, the walk will take six hours; from Wilkahuaín, four. It makes an excellent early acclimatization trip. Look for furry, rabbitlike vizcachas sniffing around and the big mountain views of the Cordillera Blanca.
At the time of writing, the hike was not being recommended due to robberies in the area. Check up-to-date on-the-ground information when you arrive.