Luft = air
Güte = quality (industrial term)
Mess- = something that is measuring
Station = station
These boxes you find all over Germany and they are measuring the quality of the air in cities. The first results they delivered were that banning cars with a higher pollution from entering the city center (you need a certain sticker on your car in Germany to enter the center) has mad NO DIFFERENCE at all. Sorry, I meant not difference for the air quality. It was compulsory to get such a sticker. And it awas compulsory to pay 5 EUR for it... great deal for the cities..
In Berlin they gave these boxes some nices designs, like this one: