Bigger on the Inside

You touch an object or structure of Medium size or larger that possesses an interior space capable of holding at least a single Small creature, such as a chest, basement, or carriage. For the spell’s duration, the interior space of the target is magically expanded to a 20-foot cube. This effect cannot be observed from the exterior of the object, which otherwise appears unchanged. When the spell ends, anything that could not fit within the dimensions of the target in its ordinary state is expelled, appearing in the nearest unoccupied spaces outside the object.

Casting this spell on the same object every day for a year makes the effect permanent.