William Callow paid his first visit to Bologna in 1840 and his last at the age of 80, during his final overseas tour.
The two towers, Asinelli and Garisenda, built between 1109 and 1119, stand at the strategic point where the old Aemilian Way (the main Roman road linking the Northern Italian plains and the coast at Rimini) entered the town. They now stand in the centre of Ponte Ravegnana Square and have become the traditional symbols of the city. Probably built by wealthy noble families, there were once over one hundred towers dominating the town's skyline; now there are only twelve, of which these are the best known. Early subsidence caused the towers to lean, although as the present watercolour illustrates, the Garisenda leans much more dramatically, so much so that in the mid-14th Century the tower was reduced in height from sixty metres to just forty seven.
In 1864, Callow exhibited another view of the towers at the Society of Painters in Watercolour. However, in that watercolour Callow concentrated on locating the towers in their surroundings and from an angle where the lean is not so obvious. In the present work, Callow is clearly engaged by the seemingly gravity defying architecture.