A short distance beyond S. Alessio is a sort of little square, adorned with trophied memorials of the knights of Malta, and occupying the site of the laurel grove (Armilustrum) which contained the tomb of Tatius. Here is the entrance of the Priorato garden, where is the famous _View of St. Peter's through the Keyhole_, admired by crowds of people on Ash-Wednesday, when the "stazione" is held at the neighbouring churches. Entering the garden (which can always be visited) we find ourselves in a beautiful avenue of old bay-trees framing the distant St. Peter's. A terrace overhanging the Tiber has an enchanting view over the river and town. In the garden is an old pepper-tree, and in a little court a picturesque palm-tree and well. From hence we can enter the church, sometimes called _S. Basilio_, sometimes _Sta. Maria Aventina_, an ancient building modernized by Cardinal Rezzonico in 1765, from the very indifferent designs of Piranesi. It contains an interesting collection of tombs, most of them belonging to the Knights of Malta; that of Bishop Spinelli is an ancient marble sarcophagus, with a relief of Minerva and the Muses. A richly sculptured ancient altar contains relics of saints found beneath the pavement of the church. The Priorato garden, so beautiful and attractive in itself, has an additional interest as that in which the famous Hildebrand (Gregory VII., 1073--80) was brought up as a boy, under the care of his uncle, who was abbot of the adjoining monastery. A massive cornice in these grounds is one of the few architectural fragments of ancient Rome existing on the Aventine. It may perhaps have belonged to the smaller temple of Diana in which Caius Gracchus took refuge, and in escaping from which, down the steep hillside, he sprained his ankle, and so was taken by his pursuers. Some buried houses were discovered and some precious vases brought to light, when Urban VIII. built the stately buttress walls which now support the hillside beyond the Priorato. The cliff below these convents is the supposed site of the cave of the giant Cacus, described by Virgil. "At specus et Caci detecta apparuit ingens Regia, et umbrosæ penitus patuere cavernæ; Non secus, ac si quâ penitus vi terra dehiscens Infernas reseret sedes, et regna recludat Pallida, dîs invisa; superque immane barathrum Cernatur, trepidentque immisso lumine manes." _Æneid_, lib. viii.