My 17th Century Dutch isn't so good but I can still look at the illustrations in Johan Picardt's 1660 book "Korte beschyvinge van eenige vergetene en verborgene Antiquiteten" eg here, here and here. Mr Picardt is considered the founding father of the study of archaeology in the Netherlands. The drawings seem to show the hunebedden being built by giants and dwarfs. But the dwarfs seem to get the raw end of the deal as the giants end up eating them. That's certainly what it looks like at any rate.
Throughout Europe and even adjacent areas there was the widespread belief in thunderstones. These peculiar stones (prehistoric flint and stone axes) were thought to have crashed into the earth during a lightning strike. Although nowadays this superstition has largely vanished, it was still widely accepted in the first half of the 20th century.
Deinse* describes this situation for the Dutch province of Overijssel, directly south of Drenthe. He reports that virtually every farmer has at least one prehistoric axe at his farm. They were believed to protect the house against lightning, as lightning never strikes the same place twice. He even reported that particular axes were believed to possess special powers. Small bits of stone were scraped off these axes and were given to children as a medicine against convulsions.
Deinse, J.J. (1925): Uit het Land van Katoen en Heide - Oudheidkundige en Folkloristische schetsen uit Twente. p102-111
This is from p25 of 'Ceci n'est pas une hache. Neolithic Depositions in the Northern Netherlands' by Karsten Wentink, 2006 - which you can read online at Google Books - it has lots of Serious archaeological information and discussion in it.
Hunebed D29 Buinen stands just 37 metres south of its twin, D28, in the same wooded area. Measuring 7.5 × 3.1 metres, this passage grave consists of a full set of eight sidestones and two endstones and still possesses two of its original three capstones and a two stone entrance portal.
Interestingly, these capstones (one of which has slipped into the interior of the grave) are exceptionally flat, and some archaeologists consider that they were once part of the same erratic boulder. If this is the case, then the hunebed builders must have possessed advanced fission techniques in order to be able to cleave the boulder in two. How is unknown, but one suggestion is that the boulder could have been repeatedly heated by fire then cooled with water until it cracked in two; another is that wedges could have been driven into existing cracks. It is a fact that many of the hunebedden throughout Drenthe are built from stones with almost perfectly flat sides.
Hunebed D28 Buinen is a medium sized monument with impressively bukly capstones. It measures 7.5 metres long by 3.4 metres wide, and is almost complete, consisting of a full set of eight sidestones and two endstones. The easternmost of the original four capstones is missing but the other three remain firmly on their supports.
Although this hunebed lies within the administrative area of the village of Buinen, it actually lies much closer to the town of Borger than to Buinen, and can be reached by following the main N374 highway for exactly one kilometre eastward from its junction with Hoofdstraat (in Borger). A walk of under 15 minutes takes you past the Vakanzieparck Hunzedal recreation park, where, on the south of the highway, surrounded by arable farmland, lies a small grassy area surrounded by mature trees. The hunebed is clearly visible beneath these trees, just 110 metres from the roadside, with its twin, D29 a further 37 metres to the south. (Note: D28 is the northernmost of this hunebed pair, and is the one you encounter first: not D29 as stated by Jane)
During a 1927 investigation of D28, Albert van Giffen discovered—in addition to the usual finds of pottery and flints—two coils of copper wire, which proved to be the oldest pieces metal jewelry ever found in Dutch soil. The copper coils indicate that some objects in use by the Funnel Beaker farmers had come from distant places, since these rings most likely originated from somewhere in either central or southwest Europe.