Soaking in the view

The rock pools that spill over this slope resemble natural travertine formations—and indeed, they're fed by warm springs that have trickled down these valley walls for millennia. But the Grutas (Grottoes) de Tolantongo resort is largely human-made, developed in the 1970s by local farmers who resolved to transform this untraveled Hidalgo hollow into a tourism destination. In addition to dozens of relaxing pools with transfixing views, visitors can head to the valley floor for a cool dip in the Tolantongo River, a mineral-rich flow shrouded by the tree canopy below.