The giant cleanroom at Airbus ITC in Friedrichshafen, Germany. I took the original video from https://www.esa.int/esatv/Videos/2022/07/Earthcare_Satellite_B-Rolls/EarthCARE_in_Airbus_cleanroom and reduced it to the parts that focus on the cleanroom itself, so you can get an impression of just how big this is.