If you live close to sea level, then you will realize what a significant effect higher elevations can have on your body upon arriving in Cusco. Doctors recommend at least two days of acclimatization before considering any strenuous activities, such as going for the popular two or four-day hikes to Machu Picchu. A nice way to spend this time would be by exploring the historic center of Lima or taking one of the many less-demanding day hikes that are available in the country. If you plan on trekking, you can read our article on the ultimate trekking guide in Peru.