Open Monumentendag

Kamerling Onnes Building and Old Observatory open during Open Monuments Day

Date

Saturday 13 September 2025 - Sunday 14 September 2025

Address

Kamerlingh Onnes Building & Old Observatory

As part of the 450 anniversary celebrations at Leiden Law School, we’ll open our doors to the public on Saturday 13 and Sunday 14 September during the 2025 Open Monuments Day.  

Throughout this weekend, everyone can admire the Kamerlingh Onnes Building (KOG) and the Old Observatory (STW) from the inside. You can learn all about the history, architecture and function of these listed monument buildings within the university and the city of Leiden.  

On Sunday 14 September, special guided tours will be given in the Old Observatory by volunteers from the Werkgroep Leidse Sterrewacht. You can also enjoy live music at both the KOG and STW on that day.  

Although registration is not required for the guided tours, visitors are asked to be prepared for possible waiting times.

More information?

More details are available on the KOG and STW pages (in Dutch) of the Open Monuments Day website.