One interesting place to visit are the United Nations. It is an intergovernamental organization that works for international cooperation.
The headquarter is in NY, the second site is in Switzerland and the third site is in Vienna, but it has several others.... Montreal, Rome, London, Paris, ...
When I visited Vienna I visited the United Nations there... you need the passport to enter there and you can enjoy a guided visit. It is really precious!! You learn a lot!
In Vienna there are two specialized agencies, the international atomic energy and the industrial development organization There, you can only visit the second... obviously! But you can seat in a meeting room like the rulers of some countries!
Just the idea of being in a part of the world with their own police, with their own rules, that does not belong to one country... it belongs to all countries!
This initial effort to work together is great and a thing that must be strengthened as difficult times are approaching. Also, we must remember the main reason why it was founded... we have to remember, to avoid repeat those dark period.
I only know another place like this in the world... The Antartida! Do you agree?