@clonosis ,
Everything are polysurfaces, which you can then convert to meshes if you need them (with Rhino’s Mesh command).
Follow the installation steps first.
Then use this example file (just change your location and radius, and turn on all the Grasshopper boolean toggles to ‘True’ in order to generate the 3D geometry).
If you already have a terrain, input it to the ‘groundTerrain_’ of the ‘OSM 3D’ component.
If you don’t have a terrain, and would like to generate one, use the ‘Terrain Generator’ component: