Ever wonder where your items go to after you donate them? They come to rest under the branches of this tree where Neopians can collect the items for free. You're welcome to visit yourself of course, just remember that there are those less fortunate than you.
During the Void Within plot, the Money Tree was a victim of the Grey Curse, and looked more like this:
The Money Tree appears in Treasure Keepers, rooted in Portal City - however, as this was part of Katya's tale, it is possible that it never really happened.
