Dolmen D21 is a portal grave. It is one of the five dolmens located near the town of Bronneger in the Dutch province of Drenthe. Of the five dolmens, D21 is the most important given the archaeological finds. It is also one of the most photogenic dolmens in the Netherlands, due to the striking tree. A few meters from dolmen D21 you can find dolmen D22, which is why they are also called twins. A short distance away is a group of three megalithic tombs (D23, D24 and D25), and there are also two Bronze Age burial mounds in the vicinity of these dolmens.