De mirabilibus urbis Romae, preserved in a single manuscript in Cambridge, England,[1] is a medieval guide in Latin to the splendours of Rome, which was written in the mid-twelfth century by a certain Magister Gregorius ("Master Gregory") of Oxford.
[6] The fourteenth-century chronicler Ranulph Higden knew the De mirabilibus urbis Romae, for he quoted from it in book I of his universal history, Polychronicon, so extensively in fact, that his manuscripts have been useful in establishing a good text of his source.
[7] Magister Gregorius, known to us only from passing remarks in his Prologue, did not depend on other accounts of Rome, though he had read De septem miraculis mundi attributed to Bede.
His references to Rome's churches are brief: Old St. Peter's Basilica and the Lateran are mentioned almost in passing, and Santa Maria Rotonda (the Pantheon) for its unusual form; he paces it off and finds the structure is 266 feet wide.
This "document of unique value which is completely independent of the Mirabilia urbis Romae, a description of Rome by a foreign traveler written from a secular and antiquarian point of view and based primarily on personal observation supplemented by the best local tradition"[8] was first reported to scholars by M. R. James, in 1917.