Machu Picchu is located high into the Andes mountain range in Peru. It is located 80km away from Cuzco. This old citadel was once the estate of an Inca emperor. Nowadays there is not much, besides some ruins, but the view from the mountain top is breathtaking. It is understandable if you want to smoke a joint while taking in the scenery. Cannabis laws in Peru are not very strict for users and you should not have much trouble getting weed during your visit to Mach Picchu.
Marijuana is illegal in Peru. but possession of small quantities of weed, meant for your own use, is decriminalized. You are allowed to carry up to 8 grams of cannabis and not get any punishment. If you have another drug on you as well, you will get in serious trouble though. It is worth mentioning that the police can be quite corrupt, so you will want to be discrete when buying and smoking weed.
Drug laws in Peru, in general, are not aimed at the users, but at the dealers, so there is no reason to worry too much. However, do use common sense and do not smoke in public.
Getting weed in Machu Picchu
While it will be hard to get weed around Machu Picchu itself, you can do that if you visit Cuzco the largest city nearby. If you do visit the city, there is a good chance you will be offered to buy weed if you walk around the more touristy places in town or in front of a club in the night. You should keep in mind that street dealers are not trustworthy and you should always ask to see the weed before giving them money, to avoid getting ripped off.