San Bernardino is about 2.6 times smaller than Vienna.

Vienna is approximately 415 sq km, while San Bernardino (map shows its 50 named neighbourhoods; the area covers the whole city) is approximately 161 sq km, making San Bernardino 38.78% the size of Vienna.
Tip: This to-scale comparison of Vienna vs. San Bernardino uses the Mercator projection, which distorts the size of regions near the poles.
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