Key West is about 7 times smaller than Lisbon.

Lisbon (map shows its 24 named neighbourhoods; the area covers the whole city) is approximately 100 sq km, while Key West (area of Key West island) is approximately 14 sq km, making Key West 13.59% the size of Lisbon.
Tip: This to-scale comparison of Lisbon vs. Key West uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.