Boston is about 1.8 times smaller than Mammoth Cave National Park.

Mammoth Cave National Park is approximately 219 km² (84 sq mi), while Boston is approximately 124 sq km, making Boston 56.73% the size of Mammoth Cave National Park.
Tip: This to-scale comparison of Mammoth Cave National Park vs. Boston uses the Mercator projection, which distorts the size of regions near the poles.
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