Avendesora , called the Tree of Life, is the last remaining chora tree. It is planted in Rhuidean. Choras were created during the Age of Legends and are genetically altered trees that give a feeling of contentment and peacefulness to those who are in close proximity to it.
Chapter 26 of book 4, The Shadow Rising. It was after Rand came out of the columns, where he learned about the Aiel's history, in Rhuidean. Mat was hanging from the Tree of Life, Avendesora.
In book four Mat went with Rand into Rhuidean in the Waste while Rand was in a Ter'angreal that was showing him the history of the Aiel people. Mat went through a Ter'angreal doorway that led him to the world of the Eelfinn, where he hoped to get answers to questions he had asked in another Ter'angreal doorway he had entered in Tear (The Aelfinn doorway). However, instead of answering questions, the Eelfinn gave Mat things he inadvertently asked for, like giving him memories from other people to fill the holes in his memory and giving him the Ter'angreal fox necklace that prevented the One Power from being used on him. He also asked for a way out of the Eelfinn world, which they provided although not in the way he would have wished. Since Mat did not set a price before asking for these things the Eelfinn set the price themselves. They took him outside of the doorway, back to Rhuidean, and hung him from Avendesora, the Tree of Life. But luckily for Mat and all us fans out there, Rand was able to get to him in time.