@weirdestate when I was in Rotterdam last year I had to swing by this area. There’s rival groups of people offering tours but I got a bad vibe from them all so instead just walked around them.
They are close to the Markthal, a street food precinct inside an arched residential building and surf school on a the Steigersgracht canal.

What Rotterdam lacks in the old-Dutch charm of Utrecht and Amsterdam (because it almost ceased to exist during WW2), it makes up for in uniqueness.
(Edit typo)