Kolsch is brewed almost exclusively in Cologneⁱ (Koln to the Germans) in Germanyⁱ.   It is basically a lager brewed with top fermenting yeast like an ale, but treated in all other respects like a lager.   The result is that a few more fruity esters end up in the finished beer.

A few breweries outside of Cologne can market their beer as Kolsch if they have a historic record of brewing the style.