During work for the laying of a new sewer in Piazza S. Lorenzo a well defined stratigraphic sequence was recorded just below the modern road surface. Evidence of an ancient open quarry was present in the form of three large grey blocks of granular tufa, shaped and partially cut from the bed-rock. Lying directly on the surface of the bed-rock was a compact dump of late Republican material, datable to the 2nd century B.C. The context also contained a plain terracotta arula which may indicate a relationship with the nearby Republican sanctuary of Hercules and Minerva, identified in the second half of the 19th century. The tufa bed-rock and Republican dump are then cut by the construction of a wall in coarse opus listatum, built directly up against the earth to terrace the lowest slopes of the Pincetto. The structure probably protected a side-street that came off the via Tiburtina, onto which the mausoleums that have come to light at various times on the northern side of the circular basilica, must have faced. The structure in opus listatum already fell into ruin between the second half of the 5th and first half of the 6th centuries A.D. when a robber trench cut into its conglomerate. The fill, apart from ceramic material, also produced a small bone plaque decorated with incised lines and “dice eyes” and two fragments of inscription, one of which shows part of a calendar. The geological and archaeological stratigraphy was cut during the construction of the piazza in front of the basilica of Honorious III. (Massimiliano Munzi)