Inside Mercedes-Benz Immendingen: The Secret City Where Cars Get Tougher, Faster

Mercedes-Benz has built a playground where engineers can push cars to their limits without guessing what the weather will do or waiting for the sun to set. At the Global Proving Ground in Immendingen, a new light testing center stretches 135 meters and stands 8 meters high, recreating an entire country road indoors so headlights can be tuned under the same conditions every single time. The asphalt even mimics an aged surface to reflect light like a real, worn road. Up to 5 cars can run side by side, with simulated oncoming traffic, vehicles ahead, reflector posts spaced every 20 meters, and movable pedestrian dummies. The company invested 10.5 million euros and spent 2 years building it, and it shows.

The same attention to detail powers the automated Heide durability circuit. Here, driving robots take over on a rough-road loop lined with potholes, bumps, cobblestones, and everything that rattles a chassis. The goal is simple: precision and repeatability while sparing human test drivers. Because the system runs around the clock, testing moves faster while applying the exact same stress to every vehicle. Depending on the model, cars must complete up to 6,000 kilometers here, which Mercedes-Benz equates to 300,000 kilometers of real-world customer use. In other words, 1 kilometer on this circuit can equal 150 kilometers on a severely broken road. The name honors a notoriously challenging track in the Lüneburg Heath that dates back to the 1950s.

What truly sets Immendingen apart is how seamlessly the physical and virtual worlds work together. The entire proving ground is scanned down to sub-millimeter detail to create a digital twin. Engineers run thousands of virtual kilometers before turning a wheel on the real track, using the data to shape load spectra for test benches and to shortlist hardware settings worth installing on prototypes. For a new model’s chassis tuning, more than 100 digital variations may be tested first; only the best make it to physical trials. It saves time, money, and resources—without sacrificing rigor.

Immendingen itself is a world in miniature. Spread across 520 hectares, it packs more than 30 dedicated test modules, 86 kilometers of road-simulating tracks, and 286 junctions. There are tight urban intersections, mountain passes with nearly 180 meters of elevation change, and surfaces ranging from cobblestones to off-road trails and motorways. Lane markings replicate Europe, the United States, China, and Japan, so advanced driver assistance systems meet global reality in one place. Special gradients range from 30 to 100 percent, and a three-lane oval with high-banked curves helps validate stability at speed. Up to 400 vehicles can be in motion at once across coordinated test programs.

Light and weather are under control, too. Immendingen uses an “artificial sun” — high-power mobile lamps originally designed for iceberg detection on Arctic ships — to stress vehicle sensors even during overcast afternoons. Dedicated systems can drench the road surface to study spray, glare, and wiper logic. The result is year-round consistency, with about 80 percent of testing formerly done on public roads now relocated to the site. That shift has shortened development lead times and reduced the carbon footprint of testing while centralizing expertise.

The place runs like a small city. There are more than 100 charging stations for electric vehicles, 12 fuel pumps for combustion vehicles, an LTE-based management and collision-warning system, and a fully equipped plant fire brigade with its own rescue service. During peak weeks, about 2,100 visiting staff join the 250 permanent employees to keep programs moving. Nature is part of the plan, too: the landscape is maintained by grazing sheep, and several llamas protect the herd from foxes. Conservation measures span several hundred hectares, with replacement forests, habitat restorations, ponds, nesting boxes, and partnerships with environmental groups. Since ground-breaking a decade ago, Mercedes-Benz has invested 200 million euros to build the site and another 200 million euros to expand it.

It is easy to call Immendingen a proving ground, but it feels closer to a development engine. Engineers can simulate dawn, make it rain, and then flip a switch to test low-sun glare ten minutes later. They can validate a headlight matrix at 135 meters indoors, drive 6,000 brutal kilometers on a robot-piloted rough loop, and verify software updates against sub-millimeter-accurate digital twins before committing to hardware. This is how you turn ideas into durable, safe, and confidence-inspiring vehicles—faster and with fewer compromises. If you enjoy deep dives into how the cars you love are actually made better, this is the kind of place that quietly shapes what we all drive next.