Turner used this page vertically both ways up for three subjects, the lower two being inverted relative to the top one. As discussed in the Introduction, Cecilia Powell has noted that fifteen of the views in this sketchbook (folios 10 recto, 11 recto, 12 verso, this page, 13 verso; D30020, D30022, D30025–D30027) are thumbnail sketches from existing prints, mostly lithographs by Jakob Alt (1789–1872), likely seen in Turner’s Vienna hotel,1 from Adolf Kunike and Alt’s Donau-Ausichten vom Ursprunge bis zum Ausflusse in Meer (‘Danube views from its source to the sea’), issued between 1819 and the mid 1820s.2
At the top are Burg Werfenstein above Struden, near the former Strudel rapids (not from an Alt print),3 east of Grein; for Turner’s sketches of the castle and the Strudel channel, see respectively under folios 31 verso and 32 recto (D30059–D30060). There is a copy of an Alt print of the scene on folio 12 verso opposite (D30025).
The other way up are the impressive ruins of Weitenegg (Alt, plate 82),4 on the north bank not far upstream from Melk. Turner did not draw the castle again directly on this journey, having sketched it in 1833 in the Salzburg and Danube book (Tate D30270–D30272; Turner Bequest CCC 72, 72a, 73). Below, also inverted, is a view of the ruins of Hausstein on its small island beside the Wirbel whirlpool (Alt, plate 71),5 east of Struden. Like the Strudel, these features no longer exist; they are shown on folios 37 recto and verso (D30070–D30071), under which 1833 sketches are also noted.