To give you guys an idea of the dutch hills... This is the route of the Elfstedentocht (eleven cities tour): a famous ice skating race last held in 1997 : r/bicycling
Skeelerroutes Achterhoek | Vind hier jouw route
Skeeler elfstedentocht: de Tocht der Tochten | Facebook
De populairste Inline Skating routes in Friesland (Nederland) | Wikiloc
Skeeleren in en om Sneek, Skeelerroutes Sneek Friesland