tree house 
noun
A structure built in the branches of a tree for children to play in.Their tribulations and accomplishments set the stage for their little baby boy to gurgle and whimper and giggle in the romantic tree house which his daddy built from vines and branches and wood from the forest....
- At the time I thought I must have landed on a poorly trimmed branch from the floorboard of the tree house.
- After Sophie came, Uncle Andy had built her a tree house within the great mass of gnarled branches.