Not on display
There are two (or possibly three) distinct components on this sketchbook page. On the right-hand side is part of a landscape view of distant coastline, probably Mergellina seen from Naples with the Posillipo Hill beyond. The central foreground building is unidentified and it is not clear whether this is part of the same vista, or a separate study. The composition continues on the opposite sheet of the double-page spread, see folio 16 (D15938).
The rough, schematic details on the far left-hand side of the page appear to depict ships docked within a port or harbour, possibly in front of the Castel Nuovo in Naples.