Mapparium at Mary Baker Eddy Library

The Mapparium is a three-story stained-glass globe that you walk through on a glass bridge — and it's one of the most disorienting, beautiful, and acoustically bizarre experiences in Boston. Built in 1935 as a geographic exhibit for the Christian Science Monitor, the 30-foot sphere shows the world's political boundaries as they existed that year, which means you're standing inside a map where Ethiopia is still called Abyssinia, India is part of the British Empire, and the Soviet Union stretches across half of Asia.

The visual effect of standing inside a globe — where you are the centre and every continent curves away from you in correct geographic proportion — is startling enough. But the acoustics are what people remember. The concave glass surface focuses sound in unexpected ways: a whisper at one end of the bridge is clearly audible at the other, 30 feet away, while someone standing next to you speaking normally sounds oddly distorted. The effect is a property of the sphere's geometry, not any deliberate engineering, and it turns the experience from a visual curiosity into something genuinely strange.

The Mapparium is housed in the Mary Baker Eddy Library, which is itself inside the Christian Science Center — a campus of buildings around a 670-foot reflecting pool that most Bostonians walk past without entering. The globe's illumination — 300 stained-glass panels lit from behind — creates colours that shift as you move across the bridge, and the frozen-in-time political map is a surprisingly effective way of understanding how dramatically the world has changed in less than a century.