There is a forest in Poland where the trees are actually made of mushrooms - Apparently.
The Białowieża Forest in Poland is a UNESCO World Heritage Site and home to the world's largest known organism, a fungus called Armillaria ostoyae. This fungus grows by sending out underground tendrils, called mycelium, which break down organic matter and absorb nutrients. In the case of the Białowieża Forest, the fungus has grown to cover an area of over 2,400 acres, making it the largest living organism on Earth.