This is by far not the only photograph showing the city wall, but one of the sharpest. There is a large number of authentic photographs of Shanghai city wall and gates in it.
New North Gate, or Porte de Montauban 障川门, at today's South Sichuan Road, opened in 1861:
(Old) West Gate 老西门, photographed by W. Saunders:
Little North Gate 拱辰门 near Dajing Pavilion 大境阁, opened in 1907:
Little East Gate 宝带门, opened in 1553 (and obviously recently renewed at the time of the photograph, c. 1910). Note the decorative brickwork around the arch:
Soldiers' cemetery adjacent to a bulwark, at the northwestern edge of the walled city; the wall's top is quite eroded:
Even the drawings and engravings capture the design correctly:
Image: Wattis Fine Art gallery.
And then there are archival photographs mistakenly identified as the walled city of Shanghai.
Double embrasures; single band of brickwork around the arch:
Very large embrasures; pointed curve of the arch:
Embrasures on every third crenellation; very wide arch: