I'm fairly astounded by the Crazy House, in Dalat, Vietnam. Sure, this isn't the first time someone's attempted to construct a giant tree trunk out of cement, but the Dalat tree really stands out.
Dang Viet Nga only spent 420 thousand on her own tree; she's the designer and engineer. And yet it it looks a hell of a lot better than the other cement tree that immediately comes to mind (though not as gigantically ambitious)...
The Disney Tree, eternally green and rising high above Animal Kingdom, is meant to represent "the circle of life"
The Dalat tree appears physically dead, dry, and sun-bleached. All branches within the house appear likewise dead. Dang Viet says that, after witnessing the destruction of pine forests and deterioration of the environment, she was inspired to raise public awareness about our delicate environment, using architecture as her medium. The resulting house is a warning of sorts.
For your perusal and enjoyment, here's a few other remarkable cement trees: