Los Angeles is about 3.8 times bigger than Rotterdam.

Rotterdam (map shows its 22 named neighbourhoods; the area covers the whole city) is approximately 319 sq km, while Los Angeles (including the city proper only) is approximately 1,215 sq km, making Los Angeles 280% larger than Rotterdam.
Tip: This to-scale comparison of Rotterdam vs. Los Angeles uses the Mercator projection, which distorts the size of regions near the poles.
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