Today Swisstopo launched the beta of their 3D Geoportal. It
uses Cesium to display their large catalog of geospatial data. They have
adopted 3D Tiles to display their 3D Buildings. The buildings were processed
with a development version of the processing engine that will eventually be
available as part of cesium.com.
Their data contains about 3 million buildings and bridges. The source data size (KML files with COLLADA) is 65GB and the 3D Tiles size is about 3 GB.
You can see the beta here: