Tree of Knowledge

The Tree of Knowledge is a 5,000 year old gigantic library tree surrounded by houses. It is located in Ohara island, which is currently a burnt land. When the World Government sent a Buster Call to destroy Ohara, the tree fell and crushed almost every historian. The tree was used by Archaeologists who were able to decypher the Poneglyphs. It is here where Nico Robin learned to read this language, unbeknownst to the professors. It´s library was the oldest construction of the One Piece world, as of yet at least.