Rome is about 1.6 times bigger than Kansas City.

Kansas City (map shows its 145 named neighbourhoods; the area covers the whole city) is approximately 815 sq km, while Rome is approximately 1,287 sq km, making Rome 58% larger than Kansas City.
Tip: This to-scale comparison of Kansas City vs. Rome uses the Mercator projection, which distorts the size of regions near the poles.
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