Back in 2006, the best way to get a large luxury SUV with real off-road ability was to buy something from Land Rover, but then Mercedes introduced the GL-Class. Built with luxury in mind, but with using knowledge gained from decades of off-road excellence with the G-Class, the new GL took the market by storm. It was comfortable, capable, and it came with several engine options. The new SUV was so impressive that it was named Motor Trend SUV of the Year in 2007. The second generation GL was released in 2012, and Mercedes made it lighter, more powerful, more fuel efficient and more luxurious. Now its 2015 and every major luxury automaker has a large three-row SUV with some semblance of off-road abilities, so does the GL-Class still have what it takes to be crowned the best? I took delivery of an up-level GL550 and spent a full week trying to beat it into submission to find out.