Of course, everyone has heard of Paris's Louvre Museum, the Metropolitan Museum of Art in New York, and the National Gallery in London. Indeed, between these three iconic institutions, nearly 20 million visitors pass through their doors each year (roughly the same number of people who currently live in Beijing, China). But what about the museums that do not adorn their halls with paintings by such masters as Rembrandt, Van Gogh, and Picasso? Are their spaces less worthy of our attention? Some might argue yes, if multimillion-dollar works of art are not on the tour then they are not interested in spending time in the museum. Others, however, might not feel the same way. And for them, AD has put together a list of the 13 best museums around the world that many have likely never heard of.