Rhuidean's glass columns are a significant feature in the world of The Wheel of Time series by Robert Jordan. These tall, transparent structures are located in the city of Rhuidean and serve as a gateway to the past, revealing important historical events and truths to those who enter them. The columns are part of a testing process for the Aiel, a warrior society, and are used to determine a person's worthiness and understanding of their heritage. Each column presents visions that can be both enlightening and challenging, shaping the identity of those who experience them.