In English, "place" can be both a noun and a verb, right? Nothing special here - in Dutch, the noun for it is "plaats", and like with lots of nouns you turn it into a verb by adding "en", which also happens to be the plural form for the noun. So "fietsen" is the noun, "plaatsen" is preceded by "te" so it is the verb in the infinitive, and you can probably guess what "verboden" means. Dead easy. (Here endeth today's lesson.)