The Ames Room is a specially constructed room that looks normal from front on. Actually, the walls and windows are trapezoids and one corner is much farther away from the observer than the other.
This illusion uses "Forced Perspective” or “Trapezoidal Shape Constancy” to fool our brains! Have a look at the shape of the floor and roof tiles from the window, then again when you go in the room itself. The trapezoid (or diamond) shapes seem square when viewed from front-on. Also called “Anamorphic”, this stretched perspective is used a lot in sign-writing on sports grounds so that from particular camera angles the logos painted on the ground appear normal even though in reality they're stretched out at unusual angles.
Production of the The Lord Of The Rings film trilogy used several Ames Room sets to make the heights of the diminutively-sized hobbits correct when standing next to the taller wizard, Gandalf.
Go inside the room as well - and get some great shots like the one pictured!