A few weeks ago I was in Berlin, which has a huge number of excellent walking tours, many of which are free (you pay a tip at the end). These covered the usual sights, as well as some more interesting less common things. At home in Oxford, your practically can't walk down Broad Street without tripping over a group waiting for one of the few different (again mostly free) walking tours to start.
I'm going to be in Rotterdam this weekend, and I was hoping to find something similar there. However, I haven't been able to find evidence of such tours there! I can find details of self-guided ones, but I ideally want to find one with someone leading a group around offering commentary, pointing out interesting things, answering questions etc.
Do such tours exist in Rotterdam? Or have I just been spoilt by Berlin and Oxford into thinking they're very common, when in fact they're perhaps a bit of an exception?