Antwerp is about 2.9 times smaller than Seoul.

Seoul is approximately 605 sq km, while Antwerp (map shows its 62 named neighbourhoods; the area covers the whole city) is approximately 208 sq km, making Antwerp 34.4% the size of Seoul.
Tip: This to-scale comparison of Seoul vs. Antwerp uses the Mercator projection, which distorts the size of regions near the poles.
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