There are 2 MTB routes each around the 50 KM at the Hoge Veluwe National Park in the Netherlands. The route is marked with the international MTB sign in black (part MTB route Apeldoorn) and green (part MTB route Rheden).
I liked the green route (Rheden) more as a MTB route. It’s more technical and features more single tracks. The route has some extra loops that are marked with the red MTB sign. These loops are optional. They always start and end on the green main route and have more tough trail elements.
Watch out you can cycle this green route in 2 directions!
The black route (Apeldoorn) has less technical and single tracks and is more sandy. But on this route I saw 3 deers and a wild boar family what made it really special. So I suggest to cycle them both. And if you want a real challenge you can complete the entire route of 100 km and conquer in total the 1000 altimeters.
You need a MTB vignette to ride this MTB route. Find more information to buy a vignette here in Dutch: https://www.natuurmonumenten.nl/mtb/vignet