A micropolis (from the Greek Mikros, small and Polis, city) is a city within another city. The city outside the micropolis is called Perforated City. characteristics
The difference is that a micropolis and its bored city have, at least, own censuses. They may be cities independent of the State (eg Vatican City), independent municipalities, an internal city-municipality, or special mention category (exempt inner-city micropolis, municipal / inner-city independence, etc.). Another rule is that an inner city can not exceed 50 km².
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