The Mayan ruins of Tulum Mexico are easily accessed by an hour long bus ride from Playa del Carmen. Once inside this pre-Colombian walled city you'll find craggy stone ruins centered inside squares of green grass and bisected by walkways, all with the groomed trampled feel of a local park. Push past the chattering teenagers and picnicking families and climb the cliffs for breathtaking views of the turquoise Caribbean Sea. Once there you can climb down the cliff to the white sand beach or you can stand at the lookout, stare at the sea and see the same view people have looked at for a 1000 years. It probably hasn't changed much in that time and there aren't many places left like that in the world. Enjoy it.