Located near the tiny, beautiful little walled town of Woudrichem, this evocative 14th-century keep has functioned as a prison, residence and toll castle; these days it hosts tourists and various cultural events. Note that tickets can be purchased with cash only.
The castle is difficult to access via public transport. From the Gorinchem train station, it's a 1.6km walk to the harbour at Binnenstad, from where you can take a water ferry or a watertaxi to the castle. Check the website for the ferry timetable; you'll need to book the water taxi in advance.