The Grutas de Mira de Aire, (Mira de Aire Caves) are the largest caves in Portugal and one of the country’s ‘Natural Wonders’. The caves are over 11,500 meters long, with the lowest point of the caves over 230 meters deep. Visitors can access around 600 meters of the caves, descending 110 meters, down 683 steps. The caves were formed over 150 million years ago, and opened to the public in 1974. A guided tour last about an hour, I could tell you it was like entering another world, this is a place where words would never capture what one sees, so I will let the photos speak for themselves.