Cecilia Powell has identified the subject of this sketch as Genzano above Lake Nemi.1 Turner’s viewpoint is a spot to the south-east of the town looking up towards the church and bell-tower of Santa Maria della Cima with the Palazzo Sforza Cesarini on the right. In the background can be seen the tree-lined road leading towards Ariccia and the northern curve of the lake. Genzano was badly damaged by bombing during the Second World War and apart from the surviving church and palace, the prospect today looks very different. The panorama continues on the opposite sheet of the double-page spread, see folio 23 verso (D15337). Similar views of the town can be found on folios 21 verso and 24 verso (D15334 and D15340).
For a general discussion of Turner’s view of Lake Nemi see folio 19 (D15329).
Powell 1984, p.422.