A client wants a scale model of a city in which to showcase a certain project. He has provided us with a 3D model of the city, however the model consists of thousands of loose elements squashed together, without clean geometry and with intersecting faces. Ofcourse, our 3D printing software doesn't accept this. Cleaning this up manually could take weeks (the image below is but one part of the whole project). Is there a way in Blender (or otherwise) to quickly turn this mess into one solid model? It doesn't need to have a pretty topology, it just needs to be closed and printable. Thanks.