Tucked in the south-western corner of Colorado, Mesa Verde has a way of reminding its visitors that natives inhabited these lands with customs and cultures vastly different from our modern practices. Not for the faint of heart, the guided tour that cuts through this old civilization requires that explorers climb several tall ladders. To this day, researchers still cannot figure out why the entire civilization just up-and-disappeared, with no clues as to why. What was especially neat about this spot was its proximity to the four corners . . . where Arizona, New Mexico, Colorado, and Utah meet. You can stand in four places at once. Even more interesting than…