This site contains the only continental Ring-Barrow with a clearly defined inner mound bank and fosse that I know of. It is dated to ~2600bc and was built by members of the Beaker people, the same people who would invade Ireland and Britain in short succession after this barrow was built. It’s my theory that barrows like this are directly ancestral to the barrows that would later dot the Irish and British countrysides!
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This is very interesting, I didn't know there were round barrows in what is now the Netherlands! On a quick look in the Dutch sources, some urns were found that were linked to the Wessex Culture in England so the barrows might have been contemporaneous. In 1948, there were 31 barrows in the area! Nowadays there are apparently 16 remaining.