The Mercedes-Benz CLS (C257), which is the third generation of the CLS-Class, is primarily assembled in Germany. Specifically, it is produced at the Mercedes-Benz plant located in Sindelfingen, which is near Stuttgart. This facility is known for manufacturing various high-end Mercedes-Benz models, ensuring high standards of quality and craftsmanship.

If you have any more questions about the CLS or other Mercedes-Benz models, feel free to ask!