The Mary Baker Eddy Library, a research center with two floors of interactive exhibits, aims to explore ideas such as liberty and spirituality through history, with a central role for Mary Baker Eddy, the founder of Christian Science. The most intriguing artifact is the Mapparium, a unique hollow globe 30 feet across. A work of both art and history, it consists of a bronze framework that connects 608 stained-glass panels. Kids especially like the weird acoustics -- the nonporous surfaces of the globe distort sound -- and the chance to "journey to the center of the earth." As you cross the glass bridge just south of the Equator, you'll see the political divisions of the world from 1932 to 1935, when the three-story-high globe was constructed.