Mapparium (world's only three-story stained-glass globe)

The Mapparium is a three-story stained-glass globe installed in 1935 inside the Mary Baker Eddy Library. Visitors walk on a glass bridge through its interior to view the painted panes that form the roughly 30-foot-diameter globe. The library describes it as the only three-story stained-glass globe in the world. The interior is noted for unusual acoustic properties that create clear whispering-gallery effects.