Cancún is a city in southeast Mexico on the northeast coast of the Yucatán Peninsula in the Mexican state of Quintana Roo. This Mexican city borders the Caribbean Sea and is best-known for its white sandy beaches, near-perfect weather, and crystal clear waters. Marvel at The Mayan city of Chichen Itza, famous for its pyramid ruins; it's both a UNESCO world heritage site and one of the Seven Wonders of the World. Cancun is also a famed destination for seeing endangered whale sharks, the largest fish in the world, about the size of a school bus.