Washington glamping has it all. From Yurts to Tents with some Domes as an additional option. With all of the trees in the state you would hope for some tree houses. Not to disappoint, check out those tree house options.
Wkipedia on tree houses:
“A tree house, tree fort or treeshed is a platform or building constructed around, next to or among the trunk or branches of one or more mature trees while above ground level. Tree houses can be used for recreation, work space, habitation, and observation.”