Puno is on Lake Titicaca. Indigenous people lived in Peru for thousands of years before the Eurpoeans arrived. They brought Catholicism with them and now about 70% of South America is Catholic.
3-5 day hike, not so difficult, except for the change in elevation... about 12000 feet ascent. Have to acclimate in Cusco for aout 2 days before hiking. 45 km trail, ends at Machu Picchu. Starts from the Scared Valley. One of the world's most famous hiking trails.