I understand that you want to create 3D models of structures or monuments. One way to do this is to use laser scanning equipment such as Faro Focus 3D to scan rooms or structures of limited height. When it comes to monuments such as Eiffel tower such solutions are not feasible.
Second method is to convert the 2D images into 3D models. Applications such as Autodesk123D can be used to convert 2D images to 3D models for the purposes of printing them. Alternatively 3D models for most of the monuments have already been created and can be downloaded by searching on Google’s 3D Warehouse