<p>A monumental mid-Republican retaining wall of <i>opus quadratum</i>, which — together with the corner of the Servian Wall — transformed the prominent cliff at the N angle of the *Aventine’s SE height (s.v. *Remoria) into a grand plateau just inside the circuit. Preserved to a height of 10 m (L. 15 m), the wall is built of Grotta Oscura tufa and travertine blocks with an articulated cornice course (Di Manzano and Quinto 69 fig. 4 no. 6, 70 with fig. 5, 75); up to the early 20th c. the wall was preserved over a considerably longer distance, apparently some 85 m (iid., 70 fig. 6, detail of Nolli map; Lanciani, <i>FUR</i> pl. 41, indicating a wall thickness of <i>c</i>. 1 m). In the 2nd c. A.D., seemingly in conjunction with the building of luxurious, perhaps imperial, residential complexes on the plateau (on this, s.v. Remoria), major drainage provisions were installed along the rear side of the wall (Di Manzano and Quinto 72-74). Addressed as an “enclosure-wall of an important complex, perhaps a sanctuary” (iid., 75), it clearly heightened the natural prominence of the cliff, which has been plausibly identified as the site dedicated to Remus of the Remoria and its <i>Saxum</i>.</p>