This sketch of the River Tiber shows the view looking upstream towards the Ponte Sisto, recognisable by the circular ‘eye’ in the centre of the bridge. During the nineteenth century this feature served as a flood warning to the people of the city. When the level of the waters reached the hole it was time to evacuate low-lying areas prone to flooding. The problem was finally addressed by the building of the Lungotevere and the embankment at the end of the century, a project which necessitated the demolition of many of the buildings lining the banks of the river seen here. Turner’s viewpoint here is probably a position near the northernmost tip of the Isola Tiberina, the island linked by bridges to the Trastevere and Jewish districts of the city. On the left it is possible to see the trees crowning the ridge of high ground known as the Janiculum Hill and on the right is the dome of St Peter’s Basilica.
The sketch is inverted on the page. A similar view can be found in the St Peter’s sketchbook (Tate D16248; Turner Bequest CLXXXVIII 51a).