Despite grumblings from the children, we got an early start this morning for the two hour trip to the ruins of Tulum. Unique as the only Mayan city to be built overlooking the ocean, it is protected by a coral reef and cliffs. We were fortunate to get another very knowledgeable and charismatic private guide who helped us understand the history and context of the Mayan civilization. Today iguanas rule the temples that were once occupied by a people who developed a more accurate calendar than the Europeans and developed a hurricane warning siren that still operates today.