Visit the ancient Maya city of Tulum early in the day and beat the crowds. Depart from Cancun for the drive to Tulum, where you'll tour the grounds with an experienced archaeologist who will fill you in on local Mayan history. Meander along the city's fortified wall, wander among temples and see the impressive el castillo. Then embark on one of two outings: explore underground caves where Mayan ceremonies were held in Xcaret or bicycle among tropical birds and go tubing in Xel-Há. Snorkel with colorful fish in both locales.