In 1933 a budget hotel and hostel Stayokay Heemskerk (booking.com) opened in the castle. We planned to stay there, but all rooms were booked. The place is quite unusual and better to book in advance.
The castle park can be visited free of charge until 18:00.
In the following photos you can see how the park looked earlier. Actually, there was no park at all.
Getting there: The castle is located 30 kilometers from the center of Amsterdam. Parking N 52 30.336 E 4 41.016. The nearest railway station is Heemskerk, then 2 km on foot. Or go to the Beverwijk station and from there by bus to the stops Heemskerk, De Weid or Heemskerk, J.v.Kuikweg. Use the route planner https://www.connexxion.nl/.