Tulum was a Mayan port city located on the coast. It is a short taxi ride or a nice bike ride from the hotel zone. The ruins are very cool and have so much history. We highly recommend you download the "Tulum Ruins Cancun Mexico" app. It is free to download, but you can pay $3 to have a guided tour through the app. The app will use your location and provide commentary to the history and architecture as you walk through the ruins. There is also a beach there if you want to swim. To avoid crowds, get there closer to 8am. The admittance fee is 80 mexican pesos per person (US$3.50). USD AND CREDIT CARD ARE NOT ACCEPTED.