Tulum, Mexico, 130km south of Cancun.
I was there in 2006.
At the time it was $6 / night to tent. $12 / night for a concrete cabana.
The only time I ever enjoyed Yoga.
The highlight for me was daily walks to the pre-Columbian Mayan walled city.

Cenotes are another local highlight.
Click PLAY or watch it on YouTube.