This reserve is at the center of the Peruvian puna, a high-altitude swath of the Andes which, at 3,900 to 4,500 meters (12,792 to 14,760 feet), is one of the highest regions in the world inhabited by humans. Its boundaries begin about 10 km (6 miles) north of the town of Junín along the shores of the lake of the same name, which, at 14 km (9 miles) wide and 30 km (19 miles) long, is Peru's second largest, after Lake Titicaca. Most visitors arrive via day tours from Tarma, but anyone traveling overland from Huánuco via Cerro de Pasco will pass through the parkland.
Flat, rolling fields cut by clear, shallow streams characterize this cold, wet region between the highest Andes peaks and the eastern rainforest. Only heavy grasses, hearty alpine flowers, and tough, tangled berry bushes survive in this harsh climate, although farmers have cultivated the warmer, lower valleys, turning them into an agricultural oasis of orchards and plantations. The mountains are threaded with cave networks long used as natural shelters by humans, who hunted the llamas, alpacas, and vicuñas that graze on the plains. The dry season is June through September, with the rains pouring in between December and March.
The reserve is also the site of the Santuario Histórico Chacamarca (Chacamarca Historical Sanctuary), an important battleground where republican forces under Simón Bolívar triumphed over the Spanish in August 1824. The battle consisted entirely of hand-to-hand combat, without firearms, and the routing of the Spanish cavalry by patriot forces virtually assured Peru's independence, which came in December of the same year at Ayacucho. A monument marks the victory spot. The sanctuary is within walking distance of Junín, and several trails lead around the lake and across the pampas.
Bird fans stop here to spot Andean geese, flamingos, and other wildlife on day trips from Tarma.