It may not look like much from the outside (with it being the HQ of the National Bank of Poland), however, inside this mundane building is one of the best museums in Warsaw. Seriously. And it's completely FREE! Enter the main gate and then the door on the left to go through airport style security, and from here you will begin your journey through the history of world economics. Again, this may sound far from exciting, but this museum is super-modern, multimedia packed and fantastically interactive - for both adults and kids! Start off learning about the history of commerce in ancient civilisations, to the importance of trade through the millenia, right up to present day. This is not just a museum about money, but of the very essence of the world system we're part of. The interactive elements are immensely informative as you walk through a safe, lift a real gold bar (not as light as they seem to be in the movies!) and learn how to spot fake bank notes. We were mightily impressed, as will you be.