Antwerp is about 30 times smaller than Shanghai.

Shanghai is approximately 6,341 sq km, while Antwerp (map shows its 62 named neighbourhoods; the area covers the whole city) is approximately 208 sq km, making Antwerp 3.28% the size of Shanghai.
Tip: This to-scale comparison of Shanghai vs. Antwerp uses the Mercator projection, which distorts the size of regions near the poles.
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