Dachau is a small city - essentially a suburb - near Munich, about 20 minutes by train. The site of the concentration camp is about a 15 minute bus ride from the Dachau train station. During the Nazi years, many of the high ranking Nazi officials had homes in Dachau.
The concentration camp at Dachau was among the first built, and served as the model for hundreds of camps. The dark labels on the map in the photo show where the main concentration camp sites were throughout Germany and occupied western Europe. All of those lighter squares were subcamps built because the main camps could not hold all of the people. The map does not reflect the Extermination Camps - Auschwitz, Treblinka, and others which were located in Poland and western Russia, and were built for the express purpose of the extermination of the Jewish population.
Although Dachau was not an extermination camp, more than 60,000 people died there during the years it was in operation. Some were executed; many were literally worked to death; others underwent a variety of "medical" experiments; and many succumbed to a combination of mistreatment, disease, starvation, and loss of hope.
There were two crematoriums at Dachau for the disposal of dead bodies. The original crematorium was built in 1939, and was not large enough to handle the volume; the second, larger one was built in 1943. There was a gas chamber in the larger crematorium - there is no record of it having been used, but it was the prototype for those used in the Extermination Camps.
The majority of prisoners at Dachau were Germans. Initially, political opponents of the Nazi party, and then an increasing number of those who were deemed "unfit" - Communists, Socialists, homosexuals, mentally and physically handicapped, Jehovah's Witnesses, and Jews. I'm reminded of Dietrich Bonhoeffer's quote
First they came for the Communists, but I was not a Communist so I did not speak out. Then they came for the Socialists and the Trade Unionists, but I was neither, so I did not speak out. Then they came for the Jews, but I was not a Jew so I did not speak out. And when they came for me, there was no one left to speak out for me.