Hi,
first off I agree with Cletus. Other things you have to consider when you create a manipulation are the perspectives and scales of all objects you want to add to your composition. If you look at the whole picture the bridge should be shown from the top, but actually the shot was taken from below the bridge so it looks weird. The statue looks as if it is just about to fall into the water because the photo was taken from a totally different angle. Also, the levels of sharpness are different. The bridge seems to be much detailed than the bushes and plants around it, which doesn't help blending at all.
Hope this was a bit helpful. 