The burdei dates back as far as 6000 years and it’s a type of half-dugout shelter somewhat between a sod house and a log cabin, usually with a floor that’s 1 – meters under ground level. Not realy a tree house but still cool
Puerto Princesa Underground River is located about 30 miles km) north of Puerto Princesa, Palawan, Philippines. On Puerto Princesa Underground River was provisionally chosen as one of the the of Nature.
Virtual books: images only - Lewis Carroll's Alice's Adventures Under Ground:The british museum offers the manuscript to read; that would later be published under the title of alices adventures in wonderland.