Near the house
Beautiful cycling routes signed by the Royal Dutch Touring Club
Sailing, canoeing, rowing on the lakes
Fishing in own water
Golf on the golfcourses of Alphen aan de Rijn and Nieuwveen
Archeon Roman Theme Park
Avifauna Bird Park

More info: here...

30 minutes by car
Amsterdam with it's canals, the Rijksmuseum and Anne Frank house
The Hague with 'the girl with the pearl earring" and Madurodam
North Sea Beach of Noordwijk or Scheveningen
Gouda with the cheese market and candle making
Leiden with a Rembrand van Rijn walking tour
Utrecht with the beautiful Dom Tower and railway museum
Keukenhof, inspirational tulip garden ( only open in spring)

Further away
Efteling, famous Anton Pieck fairy tale and fun park
Palace "het Loo" and palace gardens
Kroller Moller Museum
Open air Museum