There are multiple organisations at Leiden organising events for exchange
students. As I previously mentioned the university organised the OWL week in
the beginning of the semester. I found a lot of friends during this week with
whom I spent most of my leisure time and did some trips together during the
semester.
A few other organisations to look out for are:
Lisco -- the international committee of the student association at the
medical faculty organised events like museum trips, bowling and boat trips which
where a great way to get to know fellow international students at the LUMC.
ESN – the Erasmus Student Network organised international nights with
changing themes at a bar on Wednesdays, cocktail nights on Fridays and game
nights on Mondays.
If you are interested of any type of sport or exercise, I recommend
getting a membership at the University Sports Centre. The membership was affordable,
and you got access to multiple gyms as well as a variety of instructed classes
like yoga, different types of dancing, boxing, volleyball, and many other
sports.
Something I strongly recommend doing in your free time is travelling. There
are so many different beautiful cities in the Netherlands (I for example
visited Amsterdam, the Hague, Rotterdam and Groningen) and the train network makes
most of them easily accessible. If you are travelling in a group to a city
further away, I recommend looking up the NS group ticket, this can be a lot
cheaper than buying single tickets!