Dunn, Jerry Camarillo, Jr. (2007 online). “Machu Picchu”. How Stuff Works.com, Travel, Destinations. 2008年8月18日閲覧。 “The famous Inca Bridge is located along an ever-narrowing mountain trail that, at some places, is cut into a sheer cliff. The builders cleverly left a gap in a buttressed section of the trail that they could bridge with two logs. As needed, the logs could be removed to make the road impassable to outsiders.”
peruperuperu.com
PeruPeruPeru.com (2007年). “Day 19: Machu Picchu / Cusco”. Peru The Grand Tour, 21 Days 20 Nights (travel agency). 2007年8月18日閲覧。 “[...] hike Huayna Picchu the pyramid-shape mountain above Machu Picchu, walk to the Inca Bridge a secret entrance used by the Inca's army, or toward the Inca Trail to find the historic Sun Gate.”
xanga.com
MachuPicchuPeru (2006年1月26日). “Machu Picchu”. Machu Picchu 2006. 2008年8月18日閲覧。 “[Inca Bridge photograph] Inca Bridge - carved into the cliff”
