The Trans-Dimensional Garage is described as a naturally occurring temporal anomaly and one of only three known “dimensional plurality bubbles”. Used during James Potter's first year at Hogwarts by the delegation from Alma Aleron, it's composed of a large tent with a complicated framework of wooden support struts. During that year, it served as the storage facility for the Dodge Hornet, the Stutz Dragonfly, and the Volkswagen Beetle Flying Cars in which the AAU delegation traveled. Prof. Franklyn arrived in the Beetle, Prof. Jackson, the Dragonfly, and Prof. Delacroix, the Hornet. The tent simultaneously stood temporarily on the grounds of Hogwarts castle and in its permanent location on the east quadrangle of Alma Aleron in Philadelphia, Pennsylvania, USA.
The back of the tent appears to open onto the AAU campus. Tool chests, maintenance equipment, extra parts and workmen are all present in the garage, although they are illusory to those on the Hogwarts side. The cars are charmed to cross the dimensional bubble and exist in both places at once whenever they are inside the tent.