Hayao Miyazaki (think the Japanese version of Walt Disney) wanted to create a museum that immersed visitors into the world of his animations, and he succeeded.  The Ghibli Museum gives a glimpse into the beauty of old style animation in a whimsically designed building where you never know which character or piece of memorabilia will trigger a deep sense of nostalgia. If you're curious, check out a few of his movies: "My Neighbor Totoro", "Howl's Moving Castle", "Kiki's Delivery Service", and "Ponyo".  The museum does have a few minor inconveniences (it's situated outside of central Tokyo, tickets must be pre-purchased online, and no pictures are allowed indoors) but it's well worth checking out if you're a fan of his work.