Koningin Julianalaan, 2224 EW Katwijk
On Saturday, September 14, the national Heritage Day will take place for the 33rd time. Many monuments in Katwijk, Rijnsburg and Valkenburg will be accessible free of charge between 10 a.m. and 5 p.m.
That Saturday is also the National Organ Day and many concerts will take place.
Website (in Dutch): https://www.openmonumentendag.nl/