@ asbinzer ....You're welcome.
If your son is spending a semester in Linz, I am sure he has already walked all over the Zentrum. Aside from seeing the special exhibit offered in Schloss Linz, the view is worth it too.
If he is interested in history, the surrounding areas have some sobering sites in addition to the concentration camp. Linz itself has the WW1 and WW2 German military cemeteries. I've seen these poignant sites in Linz.
There is a memorial to the escape in 1945 undertaken by Russian POWs and who were tracked and killed by the Nazi authorities (the SS and the like) and abetted by the local population. The event is known by its horrific name, " die Hasenjagd "(hunting down rabbits) . The memorial is located along the side of a country road outside of Linz...I've seen it. There are others too, one on German POWs.
The churches in Linz are also revealing in their displaying of memorial plaques pertaining to dates important in Austrian history,,,,1848, 1859, 1866, and obviously 1914. ...just some tips should he be interested in tracking down esoteric history sites.