What impresses most is how exquisitely the sidewalks were made, with thorough details. Pay attention to the sidewalk in front of the stores. It's drawn in it something that represents the activity of the store. For example, in the sidewalk in front of an optician store was drawn a pair of glasses with white stones.
Houses also have the same care. Observing each detail you get impressed with the perfection.
Getting into the city streets you will realize that in many houses are written their age and 'name'. Many of them are from 1400s! It's really amazing to pass through places older than when Brazil was discovered!!
There is no doubt that the most famous city tourist attraction is the Freiburg Cathedral (Freiburger Müster). You can go up the tower and have a nice panorama of the city. The problem is the tiredness after climbing up all those stairs! In the day I visited it, the light sign which controls people up and down traffic was broken. Imagine the mess!J But there is no doubt it's worth!
There is also a tower in downtown that represents the typical German architecture. The trams (Straßenbahn) pass under it.
As in most of the German cities, bicycles domain as transportation mean. The German public transportation is wonderful, but also really expensive. So I believe that it's really a good investment having a bike.