It is described as a scaled model of the of the city covering almost two miles from Burnham Harbor in every direction. It is about eight feet long and a foot high. It is a meticulously detailed and accurate in its representations of everything, and is thaumaturgically connected to the city via pieces of real buildings, trees, etc. that have been placed on it. It is possible for him to be sensed while in spirit form. Also, Harry is not in touch with his body when he enters Little Chicago, and cannot tell when he is becoming exhausted. He cannot cross thresholds.