This study of the Abbey of San Paolo di Valdiponte, also known as the Abbazia or Badia Celestina, is the work of a group collaborating under the general direction of Dr. Anthony Luttrell, who is responsible for the overall co-ordination of the project. The participants have discussed each other's sections, while remaining responsible for their own contributions. The original survey of the site was made by Miss Margaret Browne, with the assistance of Miss Sheila Rixon; Figs. 2 and 3 are based upon Margaret Browne's plans, while Figs. 4, 5 and 6 are the work of Domenico Minchilli. Figs. 2, 4, 5 and 6 were prepared in their final form by M. C. Wright. The excavations, directed by Hugo Blake and Tom Blagg, are not complete. A detailed report of the seasons 1971, 1972 and 1973, accompanied by further plans, a description of the finds and a discussion of the pottery, will be published in the second part of this study; meanwhile, the present authors have been able to make full use of Hugo Blake's draft report and plans. The architecture has been studied and described by Dr. Franklin Toker, who also participated in the excavations and conducted research in archives and galleries.