Tulum means fence, trench or wall, and is the name given to the site in recent times because of the wall surrounding it, although its ancient name was possibly Zama, a corruption of Zamal (morning), associated with the dawn. This is an ideal name for the site, as sunrise in Tulum is a superb sight. The first mention of this city was made by Juan Diaz, who was on Juan de Grijalva's expedition that reached the coast of the Yucatan peninsula in 1518. He wrote, "We followed the coast day and night; on the following day... we sighted a city or town so large that Seville would not have appeared bigger or better... a very tall tower was to be seen there..." which no doubt refers to Tulum and the building known as the Castle, standing on the edge of the cliff.