Last but not least,
3. The mayan ruins of Tulum.
These ruins are located directly at the side of a completely turquoise ocean. There are small constructions inside the archeological park and there is a beach in which you may enter and stay as long as you want.
These constructions or what could be called houses are believed of being used as a port thousands of years ago by the mayan community. It is located almost two hours away from Chichen-itza.
For this place we did not get a tour guide either because we wanted to visit fast. There are some explanations available near each construction explaining their meaning, but I was not able to read all of them.
I recommend to carry with you an umbrella, sunscreen and lots of water for this visit, because the sun hits you horribly and the heat is humid. As the other archeological places, Tulum closes at 5 pm and Sundays are free entrance for mexicans. I did not pay attention which were the normal ticket prices, but surely the internet must have that information.
All these were my tips and experiences for each place I had the pleasure to visit. I hope it is useful and if you are visiting Cancun really appreciate all of its nature, culture, people and history.