This small room in the oldest building constructed for the University of Leiden would look fairly unassuming, if it weren't for the fact that it's walls are covered top-to-bottom with doctorate recipients' signatures and graffiti.
The names, dates, and other memorial markings scribbled on the walls are part of a tradition that started when the room was an antechamber where students would wait to defend their dissertations or learn the results of the doctoral exams.
As this was often an understandably nerve-wracking experience, the room came to be known as "Het Zweetkamertje" (translating literally as "The Sweat Room," or more conversationally as "The Sweating Room"). During the wait, some people chose to focus their anxious energy on doodling and putting their signatures on the walls, and a rite of passage was born.
Today, people don't have to wait as long for the results of their doctoral exams, so the signing of the wall is now done after the doctoral bull has been received. Several notable students and recipients of honorary doctorates have placed signatures here, which have been protected with little transparent plates in order to preserve them. These high-profile signatures include those of Winston Churchill, Nelson Mandela and several members of the Dutch royal family (including the current king).