hidden worlds is fabulous, and actually places environmental preservation over $$$ (they donate all profits to education)
i also suggest added coba to your list, since you can actually climb the castillo. chichen itza and tulums ruins are roped off and cannot be touched by vistors. coba is the largest and oldest city of the 3 and the castillo is magnificent, arrive before 9:30am to miss the tours from cancun before the steps are packed.
i advise anyone wanting a real eco adventure to skip anything described to be like a theme park, including xcaret, xelha, cancun and playa del carmen. eco tulum is the only place to stay, and if you really want an eco adventure not having electricity, phones, tvs, and all the modern amenties wont bother you. everything is really inexpensive here too :)
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