Apart from the photographic techniques, it's actually quite the feat to take these images with almost no people in them. Usually this is a very crowded area, especially at this time of year and at night.
If you haven't seen it already, you might also be interested in the completely restored "Altstadt" (old town, not really a historic centre). It's not very far from the location of the pictures you posted. Basically just on the other side of the river.