There is a 3D map demo where the models have been used. Each model includes both .obj and .mtl files. For example, the free and open source Three.js -library supports this format. In addition, .blend files are available that is the project file format for the free and open source Blender 3D modelling software.
The clef 3D model was created by Joseph A. Guerin and is available at the GrabCAD site.
Icons are all in the same icons.blend project file.
Please, notice that some "artistic" (read "learning 3D modelling") freedoms have been taken, so models may differ even significantly from the real landmarks.
Some landmark models also use textures:
These models can be used under CC-BY 4.0 -licence.
For example, you may write: "Includes 3D models from Erno Mäkinen, 3D icons and Tampere 3D landmark models, 2015."