Travelers to southern Peru are getting a much-needed breath of fresh air: in an effort to eliminate symptoms of altitude sickness, Hotel Monasterio, an Orient-Express Hotels property in Cuzco, has become the first hotel in the world to pipe oxygen into its guest rooms. At 11,000 feet, the 16th-century former monastery is near the ancient Incan fortress city of Machu Picchu, which draws more than a thousand visitors every day. Thirty percent of them suffer complaints ranging from headaches and irritability to breathlessness and nausea (most travelers fly in from Lima, located at sea level). Based on evidence that oxygenation of the body overnight makes you more resistant to altitude sickness the next day, the Monasterio has created an oxygen-enrichment system to serve 50 of its 128 guest rooms. Perhaps the hotel has taken its cue from Las Vegas casino owners, who, legend has it, have been pumping O2 onto their gaming floors for years to keep people alert and gambling. No word yet on slot machines at Machu Picchu.