1500 years before modern times, the place now known as the Ruins of Alph was built in Johto, and the earliest known system for writing—the modern Latin alphabet—was developed. Although no one knows exactly who built the Ruins of Alph, research indicates that the people in question were an ancient civilization that wished to co-exist with the enigmatic Unown that bear great similarity to the alphabet letters. Not only did that tribe impart messages on the ruins' walls describing the Unown, but they also erected a Pokémon statue for an unknown reason.
At some point later, outsiders began to gather near the ruins. As the Unown were timid creatures, they rejected contact with anyone but the clan that protected them. To ensure the Unown's well being, the Ruins of Alph's inhabitants decided to leave the region, but not without devising complicated puzzles so that one day the Unown could be summoned again.
-Source Bulbapedia.
