Most people are aware that CESiak offers a variety of tours into the Sian Ka'an Biosphere but this review is on their eco-lodge located inside the Biosphere, south of Tulum on the road to Punta Allen (you don't need a 4 wheel drive to get there). Revenue generated through these beautiful accommodations, tours, fishing trips and various on-site activities is used to fund conservation and education programs within the Sian Ka'an Biosphere Reserve. Unconventional and very affordable, a peaceful place to stay while in Tulum. Large tent rooms amidst the jungle sit on wooden platforms on the edge of the beach dunes overlooking the beautiful ocean. Rooms have real beds and bedding and each tent has a private covered porch w/ comfy chairs and a hammock to chill in. No electric in the tents but you are provided w/ a rechargeable lantern each night. I would suggest bringing a flashlight. The 2 bathhouses have electric lights (as does the restaurant) all generated by solar and wind power. No roughing it here - large private hot showers/dressing rooms, private toilets and sinks and free drinking water (so be sure to bring a water bottle). The views of the lagoon behind and the deserted ocean in front from the top of the bathhouse and restaurant are fabulous! Inside or outside dinning provides you with a wonderful view of the ocean and beach below. They make THE BEST pico de gallo which along with homemade chips and margaritas was our lunch many days. Food choices are varied (some local dishes) and quality is good (and getting better) and prices are average (about $30 per day per person for 3 meals). Continental breakfasts are huge and include lots of yummy local fruit so I would suggest sharing. If you email Michelle, she'll email you a menu info@cesiak.org. Rates average $60/nite PER TENT based on time of year. There is limited beach access (next to the restaurant) due to the tents being located on tall, steep sand dunes. But that location affords the breathtaking views each tent has and provides a cooling breeze on the hottest of days and nights. CESiak is a bit too far south to walk to Tulum Beach to try another restaurant, but they can be reached by bike or by car in a few minutes. If you are visiting the right time of year you can watch turtles lay eggs right on the beach at nite but first check with the staff about protocol. The staff was very accomodating and friendly and we were able to set up our Sunset Bird watching tour by boat to bird island at dusk at the front desk. Even tho it was cloudy the birds were incredible and Ben was a terrific guide who knows the Biosphere like the back of his hand pointing out not only birds, but rays and fish and plants. If you pay by credit card, be prepared for a 5% surcharge (pretty much standard in MX); but they also accept US $ or Pesos or TC's. Check out www.cesiak.org for more info on lodging and tours.