Break 19,000 Feet (December 2015)
Credit: Damian Turski / Getty Images

Get down to Ecuador and scale 19,347-foot ­Cotopaxi; it's not as technical as big glacier climbs, but it will get you acquainted with the notion that the higher you go, the worse you feel. "You need to get accustomed to those feelings in order to know the difference between 'normal' and 'fixin' to die,' " says Whittaker. You'll also expose your system to such challenges of Third World travel as fever, diarrhea, and crowded public transit – probably some gruesome combination of all three. Two-thirds of travelers to Nepal get a gastrointestinal malady within two weeks of arrival. "The culture shock and potential bacterial challenges of traveling from Kathmandu to Everest base camp have ended many a climber's trip before they even reached the mountain," says Whittaker. [EarthTreks; $2750]