Winter snow can frost the tallest peak in Hawai'i, technically weighing in at 13,800 feet. In fact, Mauna Kea holds the world record at 33,500 feet when measured from its submerged base to its summit, compared with Everest's 29,000 feet! The dormant volcano is home to the native gods and ideal for stargazing, either with the naked eye or the summit's Subaru telescope (book ahead). Go earlier and you’ll get an orange blaze—and maybe an elusive green flash—during sunset too. Note, the high altitude poses serious health risks: stop for a half hour at the visitor's station to acclimate. Plan for steep, winding roads only passable by 4WD and temperatures that can plummet to 30–40 degrees Fahrenheit. Do not visit the mountaintop within 24 hours of scuba diving.