Vilhelm Melbye - Parti fra Venedig med Dogana di Mare og bagsiden af Santa Maria delle Salute - 1857

The experts at Bruun Rasmussen read the date as 1887, which is a bit spooky, considering Melbye died in 1882. A better guess would be 1857, as there are other paintings by him from Italy from that period. That also explains the Austrian flag to the right, reminding us that Venice was under Austrian rule until 1866.