Iruya, a small town tucked in the Andes Mountains, is by far my most favorite place in northern Argentina. Located 50km off the main highway, it's not an easy ride through the mountains, but well worth it.
The locals meet everyday in the main square to chew coca leaves and socialize. Chewing coca leaves (the plant cocaine is extracted and processed from) is legal in northern Argentina, Bolivia and parts of Peru. For years the International Narcotics Control Board has tried to get the plant outlawed in these places, but has largely been ignored by the local governments. Chewing coca is a way of life in the mountains. Locals have chewed it for years to cure their altitude sickness and socialize. I tried a bit with the locals. You take a few leaves, place them in your mouth. You're then given ilucta (a preparation of the ashes of the quinoa plant). This softens the leaves and activates the alkaloids of the coca leaves. It works wonders for altitude sickness, gives you a boost of energy, and leaves your face numb - not all that different than a trip to the dentist. Coca leaves are not abused by the locals. It's rather viewed as a daily tea or coffee break and respected as a long standing tradition used by their ancestors for centuries.