Christoffer Wilhelm Eckersberg: View of the Via Sacra, Rome, 1814.
It’s astonishing how much this painting looks like a photograph—when I saw it on my dashboard, I first thought it was a photograph, till I read the caption. This photorealistic style became somewhat common fifty years later. I’d presume that painters actually often used photographs instead of sketches to prepare their painting. Here, a decade before even the crudest attempt at photography succeeded, it is rather surprising.