In the scene where young Leon is standing on the bridge in Amsterdam, you see a stock video of Amsterdam played in front of him, then when the camera is facing the front of the bridge, in the 2 shot with the other agency guy standing next to him, the background is everything but Amsterdam, it is a studio background based on Venice. The style of the building reveals the most, it doesn't fit the style of the actual Amsterdam stock footage, which you see when the camera is Point of View from Leon, over the Water.