Ciudad Perdida, Colombia
One of the world’s most challenging hikes, the trek up to Colombia’s Lost City (Ciudad Perdida) is not for the faint of heart. The hike, which can take anywhere from five to seven days, takes hikers up a staggering 3,937 feet in sticky, humid and often unpredictable South American weather. The trail weaves through narrow forest passageways, up steep and uneven paths and will even have you traversing rivers. In the dry season, the river crosses are just knee-deep, however, if you’re visiting during wet season (October/November), you may be wading through rushing rapids up to your chest. Try to spend as much time as possible at the top of the ruins, known as Teyuna, to absorb the panoramic views of the lush mountain countryside.