The Incas constructed a system of connections of almost 40,000 kilometers of trails to link the far off corners of their very large empire that reached from Quito in Ecuador down to Santiago in Chile and East to Mendoza in Argentina. Cusco was at the center of this important empire. Nearly all of the main trails in the mountains encircling Cusco were constructed or improved upon by the Incas. Still, an especially exquisite 43km portion of mountain trail linking Runcuracay, Sayacmarca, Phuyupatamarca, Wiñay Wayna and Machu Picchu has become a favourite with trekkers over the last 30 years and is known as the Inca Trail to Machu Picchu. Admission to this portion of the trail is rigidly regulated and only accredited companies can sell this hike. All guides must have a license and only a restricted amount of permits are available and must be bought some months beforehand. Always book with a legitimate company and check the itinerary thoroughly.