Pompidou Centre, Paris, France, Richard Rogers and Renzo Piano
I love this building because the experience is like an amusement park ride, fun, unexpected, extroverted but at the same time also very conceptual and satisfying intellectually. Simply put its experimental, smart and fun.
A liitle recognition to my home state Michigan (could use some love these days). We used to take tours of factories in grade school, seeing the inside of those huge linear spaces with the flurry of the assembly line was thrilling. Later in college, the factories of Albert Kahn, such as the Dodge Truck Factory and the Packard Plant were influential in the seeing the simple direct expression of form following function.
Torqued Ellipses, by Richard Serra
Sorry not a building, but wouldn't feel right without mentioning this experience. I think it was the most 'architectural' experience I've had, the awareness of my body in space was like no other. So amazingly orchestrated with one material. Its one of those things you wish eveyone could experience, because you can't describe it.... very physcial.
Photo of the Pompidou Center courtesy of Just A Slice