Nahuel Huapi National Park is in San Carlos de Bariloche, which is a city in Rio Negro, Argentina. Bariloche is one of those places you'll end up staying longer than you planned. Why? it's not for the city's aesthetic appeal, rather it's for the great outdoors and night life. It's the elite honeymoon capital in Argentina. It's the main hub for travelling around the Lake District, the gateway to Patagonia and chocolate capital of Argentina.
For National park information and a good collection of maps, visit Parque Nacional Nahuel Huapi on the corner of San Martin and Morales.Also Club Andino offers free maps and provide information on trekking area. They sell transfers and trekking packages and you can reserve a bunk there for most of the shelters in the nearby mountains.