Modern Frankfurt Zoo

Aerial view of Frankfurt Zoo in 2006. If that is the original zoo tower from the 1878 photo below, then when the 1878 picture was taken the photographer would have been standing in just about what is now the sea lion pool, shooting across, and the tower is on the wrong side of the river. Does any one know if that is the River Main running through the zoo, and was it rerouted after the war? The modern growth of tree's, which I am assuming may include some Sycamores with lumens, which we see today along the water, would have made the 1878 shot difficult, if not impossible.