This paper is intended to introduce the recent studies on the Plan of St. Gall that are against the theory of Hom and Born which is now widely accepted, and to reconsider the importance of the Plan in the carolingia architectural history. In his survey, Jacobsen made an important discovery on the Plan and made clear that the Plan church had experienced twice modifications, and concluded that the Plan was made aound 830 without any direct relation to the monastic reform synods at Aachen.
