"Dolmen" should also be accepted, in addition to "hunebed", they are synonyms.
("Dolmen" is included in "het Groene boekje".)
According to the Oxford Style Manual, a dolmen is a prehistoric tomb. Therefore, it should be dolmens because Drenthe does not have a dolmen. It has 53 of them. The rest of the Netherlands has one.
Another place for the bucket list. :-)
Is there a difference between beroemd and bekend? The answer gives both
Beroemd = famous
Bekend = (well-)known
Never heard of them
Boy, are you out of it.