The towering limestone walls of El Potrero Chico are home to world-class rock climbing, with more than 600 routes with ratings between 5.7 and 5.14. El Potrero Chico Guides (www.elpotrerochicoguides.com) charges a whopping US$340 per day for two people (not including gear, food or water) to lead visitors on climbs. Located outside of Hidalgo, about 50km north of Monterrey.