Tulum has two distinct faces: the archaeological zone perched dramatically on Caribbean cliffs, and the bohemian beach strip south of the ruins. Both are worth your time.
The ruins are the most scenically dramatic in Mexico — El Castillo pyramid sits on a 12-meter cliff above turquoise water. Arrive at 8am when gates open; by 10am the tour buses arrive and it gets crowded.
Gran Cenote is the essential Tulum experience — crystal clear blue water filtered through limestone, stalactites hanging overhead, sea turtles visible below. Use only biodegradable sunscreen; the cenote rangers enforce this.
Rent a scooter for maximum flexibility. Town and beach are 3km apart, and cenotes scatter across the jungle. Scooter rental costs MXN 300-400 per day.