Dachau Altstadt. Dachau is a city with about 44,800 citizens in Upper Bavaria, Germany and has a history of more than 1,200 years, but best known for being the location of the very first Nazi concentration camp.achau Altstadt. Dachau is a city with about 44,800 citizens in Upper Bavaria, Germany and has a history of more than 1,200 years, but best known for being the location of the very first Nazi concentration camp.