The Hoge Duvel is a beautiful 'Strade Bianche' piece of pavé / hardpack gravelroad, straight through the 'Kroondomein het Loo' forests. It's suitable for all kind of bikes, including road racers. Be aware though of some 'loose gravel' parts, keep your eyes on the road but don't forget to enjoy the beauty of the exception Dutch nature here.
Practical side note: 'Kroondomein het Loo' are the royal hunting grounds and therefore most roads are closed off to the public from mid-september to Christmas! This path is one of the exceptions though:)