Pros
Great co-workers, wonderful exposure to an international environment. I got to work with people from all over the world and was exposed to many elements of UN-affiliated organizations. I was able to help with the executive council and with the Conference of States Parties which I really enjoyed. When I was there, there was a strong commraderie among the interns in all the different divisions. It wasn't officially sponsored by the organization but we usually sat together at lunch and hung out on weekends/evenings. That being said, my department also worked hard to include me.
Cons
A bit unorganized. I relocated to Holland for this internship and was told I would be working in the library. Then when I got there and was shown to my assignment, my 'would-be' supervisor sort of threw a fit and said he 'didn't want any more interns!' Luckily, the HR department handled this very professionally and ended up adopting me for the length of my internship. I shuffled through a few assignments within HR (entitlements and benefits, recruitment, special projects) and that helped me learn a lot. Now I work in HR full time for a nonprofit in the states! Another con would be that a lot of the day to day work was boring and tedious at times (filing and paperwork. But that's sort of the nature of some jobs-especially as an intern-and overall I didn't mind).