Colmar-Berg (Luxembourgish: Colmer-Bierg, German: Colmar-Berg) is a commune and town in central Luxembourg, in the canton of Mersch. It is situated at the confluence of the rivers Attert and Alzette. As of 2005, the town of Colmar-Berg, which lies in the east of the commune, has a population of 1,711. Colmar-Berg is the site of the Grand Duke of Luxembourg's principal residence, Berg Castle. It is also the site of a Goodyear tyre factory. The commune was known as simply 'Berg' until 25 March 1991. The "Centre de Formation pour Conducteurs" (French for "Drivers' Training Centre") is also in Colmar-Berg. Every person has to make an "Obligatory Course" after they got their driving license in order for it to become a definitive license. This has to be done in the timespan after three months and before two years after the person passed their practical driving test.