Grand Canyon Field Institute | Colorado River | Machu Picchu | cable car

2 Stand At The Sun Gate
Seeing Machu Picchu is one of the world's most breathtaking experiences: Andean peaks cradling buildings of immense quarried stones. These days, you can get to the top by cable car. But to truly inhale the lost city of the Incas, one must approach it from Chilca via the Inca trail. The 33 miles over windswept river, cloud forest, and blustery mountain paths make stepping through the Sun Gate and gazing down upon one of the world's most intriguing cities so excruciatingly intoxicating, it's impossible to pen with words. Many cry. Gold was, to the Incas, the teardrops of the sun. (800) 289-9470, www.andesadventures.com

3 Crawl Into A Grand
Canyon Cave Everybody goes down the Colorado River - or stands and gapes from the Canyon Rim. Both miss the caving. Skirt the western edge of Horseshoe Mesa, then follow a barely discernible trail, and you'll find yourself squeezing through a narrow opening and into a cave that's 325 million years old. Deeper in the cave, the roof rises so high it's as if you're treading through the insides of a great sleeping beast. Turn off your flashlight and, in the dark cathedral hush, listen to the sound of rock sleeping for eternity. You might not find the cave yourself, but the Grand Canyon Field Institute's guides will. (866) 471-4435, www.grandcanyon.org/fieldinstitute

4 Hear The Symphony Of Genesis
Much ado is (rightly) made of lava - the fat black tongues creeping downward, their leading edges blushing red. But it's the sounds that make lava magic. Close your eyes and you will hear the lightest tinkling, as if someone is gently waking a chandelier: It's volcanic glass shedding off the cooling rock. Here and there is a steady hissing, like what you hear when you turn on a propane grill. These tender issuances are interrupted by the sudden whump of methane gas explosions. If you're lucky and the lava flows into the ocean, you'll hear the cataclysmic roar and hiss marking the birth of new earth. No lava is more accessible than Hawaii Volcanoes National Park's Kilauea Volcano on the Big Island. (808) 985-6000 for updates on volcanic activity, www.nps.gov/havo/