I'm a little confused on when to use circumpositions like "heen". Would this sentence have a different meaning without "heen"? I feel like I've seen examples in other lessons where only the preposition is used, like "de rivier stroomt door het landschap" or something like that.
Good question! As a native speaker of Dutch I had to do some research on that. You can leave out heen in the above sentence. Heen is merely used to fortify door or to give the sentence more emphasis. Here's some more information in Dutch on it: https://taal.vrt.be/doorheen-door.